Towers of Hanoi: Difference between revisions
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{{task|Classic CS problems and programs}}
[[Category:Recursion]]
[[Category:Games]]
;Task:
Solve the [[wp:Towers_of_Hanoi|Towers of Hanoi]] problem with recursion.
<br><br>
==
{{trans|Python}}
<syntaxhighlight lang="11l">F hanoi(ndisks, startPeg = 1, endPeg = 3) -> Void
I ndisks
hanoi(ndisks - 1, startPeg, 6 - startPeg - endPeg)
print(‘Move disk #. from peg #. to peg #.’.format(ndisks, startPeg, endPeg))
hanoi(ndisks - 1, 6 - startPeg - endPeg, endPeg)
hanoi(ndisks' 3)</syntaxhighlight>
{{out}}
<pre>
Move disk 1 from peg 1 to peg 3
Move disk 2 from peg 1 to peg 2
Move disk 1 from peg 3 to peg 2
Move disk 3 from peg 1 to peg 3
Move disk 1 from peg 2 to peg 1
Move disk 2 from peg 2 to peg 3
Move disk 1 from peg 1 to peg 3
</pre>
=={{header|360 Assembly}}==
{{trans|PL/I}}
<syntaxhighlight lang="360asm">* Towers of Hanoi 08/09/2015
HANOITOW CSECT
USING HANOITOW,R12 r12 : base register
LR R12,R15 establish base register
ST R14,SAVE14 save r14
BEGIN LH R2,=H'4' n <===
L R3,=C'123 ' stating position
BAL R14,MOVE r1=move(m,n)
RETURN L R14,SAVE14 restore r14
BR R14 return to caller
SAVE14 DS F static save r14
PG DC CL44'xxxxxxxxxxxx Move disc from pole X to pole Y'
NN DC F'0'
POLEX DS F current poles
POLEN DS F new poles
* .... recursive subroutine move(n, poles) [r2,r3]
MOVE LR R10,R11 save stackptr (r11) in r10 temp
LA R1,STACKLEN amount of storage required
GETMAIN RU,LV=(R1) allocate storage for stack
USING STACKDS,R11 make storage addressable
LR R11,R1 establish stack addressability
ST R14,SAVE14M save previous r14
ST R10,SAVE11M save previous r11
LR R1,R5 restore saved argument r5
BEGINM STM R2,R3,STACK push arguments to stack
ST R3,POLEX
CH R2,=H'1' if n<>1
BNE RECURSE then goto recurse
L R1,NN
LA R1,1(R1) nn=nn+1
ST R1,NN
XDECO R1,PG nn
MVC PG+33(1),POLEX+0 from
MVC PG+43(1),POLEX+1 to
XPRNT PG,44 print "move disk from to"
B RETURNM
RECURSE L R2,N n
BCTR R2,0 n=n-1
MVC POLEN+0(1),POLES+0 from
MVC POLEN+1(1),POLES+2 via
MVC POLEN+2(1),POLES+1 to
L R3,POLEN new poles
BAL R14,MOVE call move(n-1,from,via,to)
LA R2,1 n=1
MVC POLEN,POLES
L R3,POLEN new poles
BAL R14,MOVE call move(1,from,to,via)
L R2,N n
BCTR R2,0 n=n-1
MVC POLEN+0(1),POLES+2 via
MVC POLEN+1(1),POLES+1 to
MVC POLEN+2(1),POLES+0 from
L R3,POLEN new poles
BAL R14,MOVE call move(n-1,via,to,from)
RETURNM LM R2,R3,STACK pull arguments from stack
LR R1,R11 current stack
L R14,SAVE14M restore r14
L R11,SAVE11M restore r11
LA R0,STACKLEN amount of storage to free
FREEMAIN A=(R1),LV=(R0) free allocated storage
BR R14 return to caller
LTORG
DROP R12 base no longer needed
STACKDS DSECT dynamic area
SAVE14M DS F saved r14
SAVE11M DS F saved r11
STACK DS 0F stack
N DS F r2 n
POLES DS F r3 poles
STACKLEN EQU *-STACKDS
YREGS
END HANOITOW</syntaxhighlight>
{{out}}
<pre style="height:18ex">
1 Move disc from pole 1 to pole 3
2 Move disc from pole 1 to pole 2
3 Move disc from pole 3 to pole 2
4 Move disc from pole 1 to pole 3
5 Move disc from pole 2 to pole 1
6 Move disc from pole 2 to pole 3
7 Move disc from pole 1 to pole 3
8 Move disc from pole 1 to pole 2
9 Move disc from pole 3 to pole 2
10 Move disc from pole 3 to pole 1
11 Move disc from pole 2 to pole 1
12 Move disc from pole 3 to pole 2
13 Move disc from pole 1 to pole 3
14 Move disc from pole 1 to pole 2
15 Move disc from pole 3 to pole 2
</pre>
=={{header|6502 Assembly}}==
{{works with|Commodore}}
This should work on any Commodore 8-bit computer; just set `temp` to an appropriate zero-page location.
<syntaxhighlight lang="assembly">temp = $FB ; this works on a VIC-20 or C-64; adjust for other machines. Need two bytes zero-page space unused by the OS.
; kernal print-char routine
chrout = $FFD2
; Main Towers of Hanoi routine. To call, load the accumulator with the number of disks to move,
; the X register with the source peg (1-3), and the Y register with the target peg.
hanoi: cmp #$00 ; do nothing if the number of disks to move is zero
bne nonzero
rts
nonzero: pha ; save registers on stack
txa
pha
tya
pha
pha ; and make room for the spare peg number
; Parameters are now on the stack at these offsets:
count = $0104
source = $0103
target = $0102
spare = $0101
; compute spare rod number (6 - source - dest)
tsx
lda #6
sec
sbc source, x
sec
sbc target, x
sta spare, x
; prepare for first recursive call
tay ; target is the spare peg
tsx
lda source, x ; source is the same
sta temp ; we're using X to access the stack, so save its value here for now
lda count, x ; move count - 1 disks
sec
sbc #1
ldx temp ; now load X for call
; and recurse
jsr hanoi
; restore X and Y for print call
tsx
ldy target, x
lda source, x
tax
; print instructions to move the last disk
jsr print_move
; prepare for final recursive call
tsx
lda spare, x ; source is now spare
sta temp
lda target, x ; going to the original target
tay
lda count, x ; and again moving count-1 disks
sec
sbc #1
ldx temp
jsr hanoi
; pop our stack frame, restore registers, and return
pla
pla
tay
pla
tax
pla
rts
; constants for printing
prelude: .asciiz "MOVE DISK FROM "
interlude: .asciiz " TO "
postlude: .byte 13,0
; print instructions: move disk from (X) to (Y)
print_move:
pha
txa
pha
tya
pha
; Parameters are now on the stack at these offsets:
from = $0102
to = $0101
lda #<prelude
ldx #>prelude
jsr print_string
tsx
lda from,x
clc
adc #$30
jsr chrout
lda #<interlude
ldx #>interlude
jsr print_string
tsx
lda to,x
clc
adc #$30
jsr chrout
lda #<postlude
ldx #>postlude
jsr print_string
pla
tay
pla
tax
pla
rts
; utility routine: print null-terminated string at address AX
print_string:
sta temp
stx temp+1
ldy #0
loop: lda (temp),y
beq done_print
jsr chrout
iny
bne loop
done_print:
rts</syntaxhighlight>
{{Out}}
<pre>MOVE DISK FROM 1 TO 2
MOVE DISK FROM 1 TO 3
MOVE DISK FROM 2 TO 3
MOVE DISK FROM 1 TO 2
MOVE DISK FROM 3 TO 1
MOVE DISK FROM 3 TO 2
MOVE DISK FROM 1 TO 2
MOVE DISK FROM 1 TO 3
MOVE DISK FROM 2 TO 3
MOVE DISK FROM 2 TO 1
MOVE DISK FROM 3 TO 1
MOVE DISK FROM 2 TO 3
MOVE DISK FROM 1 TO 2
MOVE DISK FROM 1 TO 3
MOVE DISK FROM 2 TO 3</pre>
=={{header|8080 Assembly}}==
<syntaxhighlight lang="8080asm"> org 100h
lhld 6 ; Top of CP/M usable memory
sphl ; Put the stack there
lxi b,0401h ; Set up first arguments to move()
lxi d,0203h
call move ; move(4, 1, 2, 3)
rst 0 ; quit program
;;; Move B disks from C via D to E.
move: dcr b ; One fewer disk in next iteration
jz mvout ; If this was the last disk, print move and stop
push b ; Otherwise, save registers,
push d
mov a,d ; First recursive call
mov d,e
mov e,a
call move ; move(B-1, C, E, D)
pop d ; Restore registers
pop b
call mvout ; Print current move
mov a,c ; Second recursive call
mov c,d
mov d,a
jmp move ; move(B-1, D, C, E) - tail call optimization
;;; Print move, saving registers.
mvout: push b ; Save registers on stack
push d
mov a,c ; Store 'from' as ASCII digit in 'from' space
adi '0'
sta out1
mov a,e ; Store 'to' as ASCII digit in 'to' space
adi '0'
sta out2
lxi d,outstr
mvi c,9 ; CP/M call to print the string
call 5
pop d ; Restore register contents
pop b
ret
;;; Move output with placeholder for pole numbers
outstr: db 'Move disk from pole '
out1: db '* to pole '
out2: db '*',13,10,'$'</syntaxhighlight>
{{out}}
<pre>Move disk from pole 1 to pole 2
Move disk from pole 1 to pole 3
Move disk from pole 2 to pole 3
Move disk from pole 1 to pole 2
Move disk from pole 3 to pole 1
Move disk from pole 3 to pole 2
Move disk from pole 1 to pole 2
Move disk from pole 1 to pole 3
Move disk from pole 2 to pole 3
Move disk from pole 2 to pole 1
Move disk from pole 3 to pole 1
Move disk from pole 2 to pole 3
Move disk from pole 1 to pole 2
Move disk from pole 1 to pole 3
Move disk from pole 2 to pole 3
</pre>
=={{header|8086 Assembly}}==
<syntaxhighlight lang="asm"> cpu 8086
bits 16
org 100h
section .text
mov bx,0402h ; Set up first arguments to move()
mov cx,0103h ; Registers chosen s.t. CX contains output
;;; Move BH disks from CH via BL to CL
move: dec bh ; One fewer disk in next iteration
jz .out ; If this was last disk, just print move
push bx ; Save the registers for a recursive call
push cx
xchg bl,cl ; Swap the 'to' and 'via' registers
call move ; move(BH, CH, CL, BL)
pop cx ; Restore the registers from the stack
pop bx
call .out ; Print the move
xchg ch,bl ; Swap the 'from' and 'via' registers
jmp move ; move(BH, BL, CH, CL)
;;; Print the move
.out: mov ax,'00' ; Add ASCII 0 to both 'from' and 'to'
add ax,cx ; in one 16-bit operation
mov [out1],ah ; Store 'from' field in output
mov [out2],al ; Store 'to' field in output
mov dx,outstr ; MS-DOS system call to print string
mov ah,9
int 21h
ret
section .data
outstr: db 'Move disk from pole '
out1: db '* to pole '
out2: db '*',13,10,'$'</syntaxhighlight>
{{out}}
<pre>Move disk from pole 1 to pole 2
Move disk from pole 1 to pole 3
Move disk from pole 2 to pole 3
Move disk from pole 1 to pole 2
Move disk from pole 3 to pole 1
Move disk from pole 3 to pole 2
Move disk from pole 1 to pole 2
Move disk from pole 1 to pole 3
Move disk from pole 2 to pole 3
Move disk from pole 2 to pole 1
Move disk from pole 3 to pole 1
Move disk from pole 2 to pole 3
Move disk from pole 1 to pole 2
Move disk from pole 1 to pole 3
Move disk from pole 2 to pole 3
</pre>
=={{header|8th}}==
<syntaxhighlight lang="forth">
5 var, disks
var sa
var sb
var sc
: save sc ! sb ! sa ! disks ! ;
: get sa @ sb @ sc @ ;
: get2 get swap ;
: hanoi
save disks @ not if ;; then
disks @ get
disks @ n:1- get2 hanoi save
cr
" move a ring from " . sa @ . " to " . sb @ .
disks @ n:1- get2 rot hanoi
;
" Tower of Hanoi, with " . disks @ . " rings: " .
disks @ 1 2 3 hanoi cr bye
</syntaxhighlight>
=={{header|ABC}}==
<syntaxhighlight lang="ABC">HOW TO MOVE n DISKS FROM src VIA via TO dest:
IF n>0:
MOVE n-1 DISKS FROM src VIA dest TO via
WRITE "Move disk from pole", src, "to pole", dest/
MOVE n-1 DISKS FROM via VIA dest TO src
MOVE 4 DISKS FROM 1 VIA 2 TO 3</syntaxhighlight>
{{out}}
<pre>Move disk from pole 1 to pole 2
Move disk from pole 1 to pole 3
Move disk from pole 2 to pole 1
Move disk from pole 1 to pole 2
Move disk from pole 3 to pole 2
Move disk from pole 3 to pole 1
Move disk from pole 2 to pole 3
Move disk from pole 1 to pole 3
Move disk from pole 2 to pole 1
Move disk from pole 2 to pole 3
Move disk from pole 1 to pole 2
Move disk from pole 2 to pole 1
Move disk from pole 3 to pole 1
Move disk from pole 3 to pole 2
Move disk from pole 1 to pole 3</pre>
=={{header|Action!}}==
{{Trans|Tiny BASIC}}...via PL/M
<syntaxhighlight lang="action!">
;;; Iterative Towers of Hanoi; translated from Tiny BASIC via PL/M
;;;
DEFINE NUMBER_OF_DISCS = "4"
PROC Main()
INT d, n, x
n = 1
FOR d = 1 TO NUMBER_OF_DISCS DO
n = n + n
OD
FOR x = 1 TO n - 1 DO
; as with Algol W, PL/M, Action! has bit and MOD operators
Print( "Move disc on peg " )
Put( '1 + ( ( x AND ( x - 1 ) ) MOD 3 ) )
Print( " to peg " )
Put( '1 + ( ( ( x OR ( x - 1 ) ) + 1 ) MOD 3 ) )
PutE()
OD
RETURN
</syntaxhighlight>
{{out}}
<pre>
Move disc on peg 1 to peg 3
Move disc on peg 1 to peg 2
Move disc on peg 3 to peg 2
Move disc on peg 1 to peg 3
Move disc on peg 2 to peg 1
Move disc on peg 2 to peg 3
Move disc on peg 1 to peg 3
Move disc on peg 1 to peg 2
Move disc on peg 3 to peg 2
Move disc on peg 3 to peg 1
Move disc on peg 2 to peg 1
Move disc on peg 3 to peg 2
Move disc on peg 1 to peg 3
Move disc on peg 1 to peg 2
Move disc on peg 3 to peg 2
</pre>
=={{header|ActionScript}}==
<syntaxhighlight lang="actionscript">public function move(n:int, from:int, to:int, via:int):void
{
if (n > 0)
{
move(n - 1, from, via, to);
trace("Move disk from pole " + from + " to pole " + to);
move(n - 1, via, to, from);
}
}</syntaxhighlight>
=={{header|Ada}}==
<syntaxhighlight lang="ada">with Ada.Text_Io; use Ada.Text_Io;
procedure Towers is
type Pegs is (Left, Center, Right);
procedure Hanoi (Ndisks : Natural; Start_Peg : Pegs := Left; End_Peg : Pegs := Right; Via_Peg : Pegs := Center) is
begin
if Ndisks > 0 then
Hanoi(Ndisks - 1, Start_Peg, Via_Peg, End_Peg);
Put_Line("Move disk" & Natural'Image(Ndisks) & " from " & Pegs'Image(Start_Peg) & " to " & Pegs'Image(End_Peg));
Hanoi(Ndisks - 1, Via_Peg, End_Peg, Start_Peg);
end if;
end Hanoi;
begin
Hanoi(4);
end Towers;</syntaxhighlight>
=={{header|Agena}}==
<syntaxhighlight lang="agena">move := proc(n::number, src::number, dst::number, via::number) is
if n > 0 then
move(n - 1, src, via, dst)
print(src & ' to ' & dst)
move(n - 1, via, dst, src)
fi
end
move(4, 1, 2, 3)</syntaxhighlight>
=={{header|ALGOL 60}}==
<syntaxhighlight lang="algol60">begin
procedure movedisk(n, f, t);
integer n, f, t;
begin
outstring (1, "Move disk from");
outinteger(1, f);
outstring (1, "to");
outinteger(1, t);
outstring (1, "\n");
end;
procedure dohanoi(n, f, t, u);
integer n, f, t, u;
begin
if n < 2 then
movedisk(1, f, t)
else
begin
dohanoi(n - 1, f, u, t);
movedisk(1, f, t);
dohanoi(n - 1, u, t, f);
end;
end;
dohanoi(4, 1, 2, 3);
outstring(1,"Towers of Hanoi puzzle completed!")
end</syntaxhighlight>
{{out}}
<pre>Move disk from 1 to 3
Move disk from 1 to 2
Move disk from 3 to 2
Move disk from 1 to 3
Move disk from 2 to 1
Move disk from 2 to 3
Move disk from 1 to 3
Move disk from 1 to 2
Move disk from 3 to 2
Move disk from 3 to 1
Move disk from 2 to 1
Move disk from 3 to 2
Move disk from 1 to 3
Move disk from 1 to 2
Move disk from 3 to 2
Towers of Hanoi puzzle completed!</pre>
=={{header|ALGOL 68}}==
<syntaxhighlight lang="algol68">PROC move = (INT n, from, to, via) VOID:
IF n > 0 THEN
move(n - 1, from, via, to);
printf(($"Move disk from pole "g" to pole "gl$, from, to));
move(n - 1, via, to, from)
FI
;
main: (
move(4, 1,2,3)
)</syntaxhighlight>
COMMENT Disk number is also printed in this code (works with a68g): COMMENT
<syntaxhighlight lang="algol68">
PROC move = (INT n, from, to, via) VOID:
IF n > 0 THEN
move(n - 1, from, via, to);
printf(($"Move disk "g" from pole "g" to pole "gl$, n, from, to));
move(n - 1, via, to, from)
FI ;
main: (
move(4, 1,2,3)
)
</syntaxhighlight>
=={{header|ALGOL-M}}==
<syntaxhighlight lang="algolm">begin
procedure move(n, src, via, dest);
integer n;
string(1) src, via, dest;
begin
if n > 0 then
begin
writeon(" to pole ");
writeon(dest);
move(n-1, via, src, dest);
end;
end;
move(4, "1", "2", "3");
end</syntaxhighlight>
{{out}}
<pre>Move disk from pole 1 to pole 2
Move disk from pole 1 to pole 3
Move disk from pole 2 to pole 3
Move disk from pole 1 to pole 2
Move disk from pole 3 to pole 1
Move disk from pole 3 to pole 2
Move disk from pole 1 to pole 2
Move disk from pole 1 to pole 3
Move disk from pole 2 to pole 3
Move disk from pole 2 to pole 1
Move disk from pole 3 to pole 1
Move disk from pole 2 to pole 3
Move disk from pole 1 to pole 2
Move disk from pole 1 to pole 3
Move disk from pole 2 to pole 3</pre>
=={{header|ALGOL W}}==
===Recursive===
Following Agena, Algol 68, AmigaE...
<syntaxhighlight lang="pascal">begin
procedure move ( integer value n, from, to, via ) ;
if n > 0 then begin
move( n - 1, from, via, to );
write( i_w := 1, s_w := 0, "Move disk from peg: ", from, " to peg: ", to );
move( n - 1, via, to, from )
end move ;
move( 4, 1, 2, 3 )
end.</syntaxhighlight>
===Iterative===
{{Trans|Tiny BASIC}}
<syntaxhighlight lang="pascal">begin % iterative towers of hanoi - translated from Tiny Basic %
integer d, n;
while begin writeon( "How many disks? " );
read( d );
d < 1 or d > 10
end
do begin end;
n := 1;
while d not = 0 do begin
d := d - 1;
n := 2 * n
end;
for x := 1 until n - 1 do begin
integer s, t;
% Algol W has the necessary bit and modulo operators so these are used here %
% instead of implementing them via subroutines %
s := number( bitstring( x ) and bitstring( x - 1 ) ) rem 3;
t := ( number( bitstring( x ) or bitstring( x - 1 ) ) + 1 ) rem 3;
write( i_w := 1, s_w := 0, "Move disc on peg ", s + 1, " to peg ", t + 1 )
end
end.</syntaxhighlight>
=={{header|AmigaE}}==
<syntaxhighlight lang="amigae">PROC move(n, from, to, via)
IF n > 0
move(n-1, from, via, to)
WriteF('Move disk from pole \d to pole \d\n', from, to)
move(n-1, via, to, from)
ENDIF
ENDPROC
PROC main()
move(4, 1,2,3)
ENDPROC</syntaxhighlight>
=={{header|Amazing Hopper}}==
<syntaxhighlight lang="amazing hopper">
#include <hopper.h>
#proto hanoi(_X_,_Y_,_Z_,_W_)
main:
get arg number (2,discos)
{discos}!neg? do{fail=0,mov(fail),{"I need a positive (or zero) number here, not: ",fail}println,exit(0)}
pos? do{
_hanoi( discos, "A", "B", "C" )
}
exit(0)
.locals
hanoi(discos,inicio,aux,fin)
iif( {discos}eqto(1), {inicio, "->", fin, "\n"};print, _hanoi({discos}minus(1), inicio,fin,aux);\
{inicio, "->", fin, "\n"};print;\
_hanoi({discos}minus(1), aux, inicio, fin))
back
</syntaxhighlight>
{{out}}
<pre>
For 4 discs:
A->B
A->C
B->C
A->B
C->A
C->B
A->B
A->C
B->C
B->A
C->A
B->C
A->B
A->C
B->C
</pre>
=={{header|APL}}==
{{works with|Dyalog APL}}
<syntaxhighlight lang="apl">hanoi←{
move←{
n from to via←⍵
n≤0:⍬
l←∇(n-1) from via to
r←∇(n-1) via to from
l,(⊂from to),r
}
'⊂Move disk from pole ⊃,I1,⊂ to pole ⊃,I1'⎕FMT↑move ⍵
}</syntaxhighlight>
{{out}}
<pre> hanoi 4 1 2 3
Move disk from pole 1 to pole 3
Move disk from pole 1 to pole 2
Move disk from pole 3 to pole 2
Move disk from pole 1 to pole 3
Move disk from pole 2 to pole 1
Move disk from pole 2 to pole 3
Move disk from pole 1 to pole 3
Move disk from pole 1 to pole 2
Move disk from pole 3 to pole 2
Move disk from pole 3 to pole 1
Move disk from pole 2 to pole 1
Move disk from pole 3 to pole 2
Move disk from pole 1 to pole 3
Move disk from pole 1 to pole 2
Move disk from pole 3 to pole 2</pre>
=={{header|AppleScript}}==
<syntaxhighlight lang="applescript">--------------------- TOWERS OF HANOI --------------------
-- hanoi :: Int -> (String, String, String) -> [(String, String)]
on hanoi(n, abc)
script go
on |λ|(n, {x, y, z})
if n > 0 then
set m to n - 1
|λ|(m, {x, z, y}) & ¬
{{x, y}} & |λ|(m, {z, y, x})
else
{}
end if
end |λ|
end script
go's |λ|(n, abc)
end hanoi
--------------------------- TEST -------------------------
on run
unlines(map(intercalate(" -> "), ¬
hanoi(3, {"left", "right", "mid"})))
end run
-------------------- GENERIC FUNCTIONS -------------------
-- intercalate :: String -> [String] -> String
on intercalate(delim)
script
on |λ|(xs)
set {dlm, my text item delimiters} to ¬
{my text item delimiters, delim}
set s to xs as text
set my text item delimiters to dlm
s
end |λ|
end script
end intercalate
-- Lift 2nd class handler function into 1st class script wrapper
-- mReturn :: First-class m => (a -> b) -> m (a -> b)
on mReturn(f)
if class of f is script then
f
else
script
property |λ| : f
end script
end if
end mReturn
-- map :: (a -> b) -> [a] -> [b]
on map(f, xs)
tell mReturn(f)
set lng to length of xs
set lst to {}
repeat with i from 1 to lng
set end of lst to |λ|(item i of xs, i, xs)
end repeat
return lst
end tell
end map
-- unlines :: [String] -> String
on unlines(xs)
set {dlm, my text item delimiters} to ¬
{my text item delimiters, linefeed}
set str to xs as text
set my text item delimiters to dlm
str
end unlines</syntaxhighlight>
{{Out}}
<pre>left -> right
left -> mid
right -> mid
left -> right
mid -> left
mid -> right
left -> right</pre>
----
More illustratively:
''(I've now eliminated the recursive ''|move|()'' handler's tail calls. So it's now only called 2 ^ (n - 1) times as opposed to 2 ^ (n + 1) - 1 with full recursion. The maximum call depth of n is only reached once, whereas with full recursion, the maximum depth was n + 1 and this was reached 2 ^ n times.)''
<syntaxhighlight lang="applescript">on hanoi(n, source, target)
set t1 to tab & "tower 1: " & tab
set t2 to tab & "tower 2: " & tab
set t3 to tab & "tower 3: " & tab
script o
property m : 0
property tower1 : {}
property tower2 : {}
property tower3 : {}
property towerRefs : {a reference to tower1, a reference to tower2, a reference to tower3}
property process : missing value
on |move|(n, source, target)
set aux to 6 - source - target
repeat with n from n to 2 by -1 -- Tail call elimination repeat.
|move|(n - 1, source, aux)
set end of item target of my towerRefs to n
tell item source of my towerRefs to set its contents to reverse of rest of its reverse
set m to m + 1
set end of my process to ¬
{(m as text) & ". move disc " & n & (" from tower " & source) & (" to tower " & target & ":"), ¬
t1 & tower1, ¬
t2 & tower2, ¬
t3 & tower3}
tell source
set source to aux
set aux to it
end tell
end repeat
-- Specific code for n = 1:
set end of item target of my towerRefs to 1
tell item source of my towerRefs to set its contents to reverse of rest of its reverse
set m to m + 1
set end of my process to ¬
{(m as text) & ". move disc 1 from tower " & source & (" to tower " & target & ":"), ¬
t1 & tower1, ¬
t2 & tower2, ¬
t3 & tower3}
end |move|
end script
repeat with i from n to 1 by -1
set end of item source of o's towerRefs to i
end repeat
set astid to AppleScript's text item delimiters
set AppleScript's text item delimiters to ", "
set o's process to {"Starting with " & n & (" discs on tower " & (source & ":")), ¬
t1 & o's tower1, t2 & o's tower2, t3 & o's tower3}
if (n > 0) then tell o to |move|(n, source, target)
set end of o's process to "That's it!"
set AppleScript's text item delimiters to linefeed
set process to o's process as text
set AppleScript's text item delimiters to astid
return process
end hanoi
-- Test:
set numberOfDiscs to 3
set sourceTower to 1
set destinationTower to 2
hanoi(numberOfDiscs, sourceTower, destinationTower)</syntaxhighlight>
{{Out}}
<pre>"Starting with 3 discs on tower 1:
tower 1: 3, 2, 1
tower 2:
tower 3:
1. move disc 1 from tower 1 to tower 2:
tower 1: 3, 2
tower 2: 1
tower 3:
2. move disc 2 from tower 1 to tower 3:
tower 1: 3
tower 2: 1
tower 3: 2
3. move disc 1 from tower 2 to tower 3:
tower 1: 3
tower 2:
tower 3: 2, 1
4. move disc 3 from tower 1 to tower 2:
tower 1:
tower 2: 3
tower 3: 2, 1
5. move disc 1 from tower 3 to tower 1:
tower 1: 1
tower 2: 3
tower 3: 2
6. move disc 2 from tower 3 to tower 2:
tower 1: 1
tower 2: 3, 2
tower 3:
7. move disc 1 from tower 1 to tower 2:
tower 1:
tower 2: 3, 2, 1
tower 3:
That's it!"</pre>
=={{header|ARM Assembly}}==
<syntaxhighlight lang="text">.text
.global _start
_start: mov r0,#4 @ 4 disks,
mov r1,#1 @ from pole 1,
mov r2,#2 @ via pole 2,
mov r3,#3 @ to pole 3.
bl move
mov r0,#0 @ Exit to Linux afterwards
mov r7,#1
swi #0
@@@ Move r0 disks from r1 via r2 to r3
move: subs r0,r0,#1 @ One fewer disk in next iteration
beq show @ If last disk, just print move
push {r0-r3,lr} @ Save all the registers incl. link register
eor r2,r2,r3 @ Swap the 'to' and 'via' registers
eor r3,r2,r3
eor r2,r2,r3
bl move @ Recursive call
pop {r0-r3} @ Restore all the registers except LR
bl show @ Show current move
eor r1,r1,r3 @ Swap the 'to' and 'via' registers
eor r3,r1,r3
eor r1,r1,r3
pop {lr} @ Restore link register
b move @ Tail call
@@@ Show move
show: push {r0-r3,lr} @ Save all the registers
add r1,r1,#'0 @ Write the source pole
ldr lr,=spole
strb r1,[lr]
add r3,r3,#'0 @ Write the destination pole
ldr lr,=dpole
strb r3,[lr]
mov r0,#1 @ 1 = stdout
ldr r1,=moves @ Pointer to string
ldr r2,=mlen @ Length of string
mov r7,#4 @ 4 = Linux write syscall
swi #0 @ Print the move
pop {r0-r3,pc} @ Restore all the registers and return
.data
moves: .ascii "Move disk from pole "
spole: .ascii "* to pole "
dpole: .ascii "*\n"
mlen = . - moves</syntaxhighlight>
{{out}}
<pre>Move disk from pole 1 to pole 2
Move disk from pole 1 to pole 3
Move disk from pole 3 to pole 1
Move disk from pole 1 to pole 2
Move disk from pole 2 to pole 3
Move disk from pole 2 to pole 1
Move disk from pole 1 to pole 2
Move disk from pole 1 to pole 3
Move disk from pole 3 to pole 1
Move disk from pole 3 to pole 2
Move disk from pole 2 to pole 3
Move disk from pole 3 to pole 1
Move disk from pole 1 to pole 2
Move disk from pole 1 to pole 3
Move disk from pole 3 to pole 1</pre>
=={{header|Arturo}}==
{{trans|D}}
<syntaxhighlight lang="rebol">hanoi: function [n f dir via][
if n>0 [
hanoi n-1 f via dir
print ["Move disk" n "from" f "to" dir]
hanoi n-1 via dir f
]
]
hanoi 3 'L 'M 'R</syntaxhighlight>
{{out}}
<pre>Move disk 1 from L to M
Move disk 2 from L to R
Move disk 1 from M to R
Move disk 3 from L to M
Move disk 1 from R to L
Move disk 2 from R to M
Move disk 1 from L to M</pre>
=={{header|AutoHotkey}}==
<syntaxhighlight lang="autohotkey">move(n, from, to, via) ;n = # of disks, from = start pole, to = end pole, via = remaining pole
{
if (n = 1)
{
msgbox , Move disk from pole %from% to pole %to%
}
else
{
move(n-1, from, via, to)
move(1, from, to, via)
move(n-1, via, to, from)
}
}
move(64, 1, 3, 2)</syntaxhighlight>
=={{header|AutoIt}}==
<syntaxhighlight lang="autoit">Func move($n, $from, $to, $via)
If ($n = 1) Then
ConsoleWrite(StringFormat("Move disk from pole "&$from&" To pole "&$to&"\n"))
Else
move($n - 1, $from, $via, $to)
move(1, $from, $to, $via)
move($n - 1, $via, $to, $from)
EndIf
EndFunc
move(4, 1,2,3)</syntaxhighlight>
=={{header|AWK}}==
{{trans|Logo}}
<syntaxhighlight lang="awk">$ awk 'func hanoi(n,f,t,v){if(n>0){hanoi(n-1,f,v,t);print(f,"->",t);hanoi(n-1,v,t,f)}}
BEGIN{hanoi(4,"left","middle","right")}'</syntaxhighlight>
{{out}}
<pre>left -> right
left -> middle
right -> middle
left -> right
middle -> left
middle -> right
left -> right
left -> middle
right -> middle
right -> left
middle -> left
right -> middle
left -> right
left -> middle
right -> middle</pre>
=={{header|BASIC}}==
===Using a Subroutine===
{{works with|FreeBASIC}}
{{works with|RapidQ}}
<syntaxhighlight lang="freebasic">SUB move (n AS Integer, fromPeg AS Integer, toPeg AS Integer, viaPeg AS Integer)
IF n>0 THEN
move n-1, fromPeg, viaPeg, toPeg
PRINT "Move disk from "; fromPeg; " to "; toPeg
move n-1, viaPeg, toPeg, fromPeg
END IF
END SUB
move 4,1,2,3</syntaxhighlight>
===Using <code>GOSUB</code>s===
Here's an example of implementing recursion in an old BASIC that only has global variables:
{{works with|Applesoft BASIC}}
{{works with|Chipmunk Basic}}
{{works with|Commodore BASIC}}
{{works with|GW-BASIC}}
{{works with|MSX_BASIC}}
<syntaxhighlight lang="gwbasic">10 DEPTH=4: REM SHOULD EQUAL NUMBER OF DISKS
20 DIM N(DEPTH), F(DEPTH), T(DEPTH), V(DEPTH): REM STACK PER PARAMETER
30 SP = 0: REM STACK POINTER
40 N(SP) = 4: REM START WITH 4 DISCS
50 F(SP) = 1: REM ON PEG 1
60 T(SP) = 2: REM MOVE TO PEG 2
70 V(SP) = 3: REM VIA PEG 3
80 GOSUB 100
90 END
99 REM MOVE SUBROUTINE
100 IF N(SP) = 0 THEN RETURN
110 OS = SP: REM STORE STACK POINTER
120 SP = SP + 1: REM INCREMENT STACK POINTER
130 N(SP) = N(OS) - 1: REM MOVE N-1 DISCS
140 F(SP) = F(OS) : REM FROM START PEG
150 T(SP) = V(OS) : REM TO VIA PEG
160 V(SP) = T(OS) : REM VIA TO PEG
170 GOSUB 100
180 OS = SP - 1: REM OS WILL HAVE CHANGED
190 PRINT "MOVE DISC FROM"; F(OS); "TO"; T(OS)
200 N(SP) = N(OS) - 1: REM MOVE N-1 DISCS
210 F(SP) = V(OS) : REM FROM VIA PEG
220 T(SP) = T(OS) : REM TO DEST PEG
230 V(SP) = F(OS) : REM VIA FROM PEG
240 GOSUB 100
250 SP = SP - 1 : REM RESTORE STACK POINTER FOR CALLER
260 RETURN</syntaxhighlight>
===Using binary method===
{{works with|Chipmunk Basic}}
{{works with|Commodore BASIC}}
Very fast version in BASIC V2 on Commodore C-64
{{works with|MSX_BASIC}}
<syntaxhighlight lang="gwbasic"> 10 DEF FNM3(X)=X-INT(X/3)*3:REM MODULO 3
20 N=4:GOSUB 100
30 END
99 REM HANOI
100 :FOR M=1 TO 2^N-1
110 ::PRINT MID$(STR$(M),2);":",FNM3(M AND M-1)+1;"TO";FNM3((M OR M-1)+1)+1
130 :NEXT M
140 RETURN</syntaxhighlight>
{{out}}
<pre>1: 1 TO 3
2: 1 TO 2
3: 3 TO 2
4: 1 TO 3
5: 2 TO 1
6: 2 TO 3
7: 1 TO 3
8: 1 TO 2
9: 3 TO 2
10: 3 TO 1
11: 2 TO 1
12: 3 TO 2
13: 1 TO 3
14: 1 TO 2
15: 3 TO 2 </pre>
==={{header|BASIC256}}===
<syntaxhighlight lang="basic256">call move(4,1,2,3)
print "Towers of Hanoi puzzle completed!"
end
subroutine move (n, fromPeg, toPeg, viaPeg)
if n>0 then
call move(n-1, fromPeg, viaPeg, toPeg)
print "Move disk from "+fromPeg+" to "+toPeg
call move(n-1, viaPeg, toPeg, fromPeg)
end if
end subroutine</syntaxhighlight>
{{out}}
<pre>
Move disk from 1 to 3
Move disk from 1 to 2
Move disk from 3 to 2
Move disk from 1 to 3
Move disk from 2 to 1
Move disk from 2 to 3
Move disk from 1 to 3
Move disk from 1 to 2
Move disk from 3 to 2
Move disk from 3 to 1
Move disk from 2 to 1
Move disk from 3 to 2
Move disk from 1 to 3
Move disk from 1 to 2
Move disk from 3 to 2
Towers of Hanoi puzzle completed!
</pre>
==={{header|IS-BASIC}}===
<syntaxhighlight lang="is-basic">100 PROGRAM "Hanoi.bas"
110 CALL HANOI(4,1,3,2)
120 DEF HANOI(DISK,FRO,TO,WITH)
130 IF DISK>0 THEN
140 CALL HANOI(DISK-1,FRO,WITH,TO)
150 PRINT "Move disk";DISK;"from";FRO;"to";TO
160 CALL HANOI(DISK-1,WITH,TO,FRO)
170 END IF
180 END DEF</syntaxhighlight>
=={{header|Batch File}}==
<syntaxhighlight lang="dos">@echo off
setlocal enabledelayedexpansion
%==The main thing==%
%==First param - Number of disks==%
%==Second param - Start pole==%
%==Third param - End pole==%
%==Fourth param - Helper pole==%
call :move 4 START END HELPER
echo.
pause
exit /b 0
%==The "function"==%
:move
setlocal
set n=%1
set from=%2
set to=%3
set via=%4
if %n% gtr 0 (
set /a x=!n!-1
call :move !x! %from% %via% %to%
echo Move top disk from pole %from% to pole %to%.
call :move !x! %via% %to% %from%
)
exit /b 0</syntaxhighlight>
{{Out}}
<pre>Move top disk from pole START to pole HELPER.
Move top disk from pole START to pole END.
Move top disk from pole HELPER to pole END.
Move top disk from pole START to pole HELPER.
Move top disk from pole END to pole START.
Move top disk from pole END to pole HELPER.
Move top disk from pole START to pole HELPER.
Move top disk from pole START to pole END.
Move top disk from pole HELPER to pole END.
Move top disk from pole HELPER to pole START.
Move top disk from pole END to pole START.
Move top disk from pole HELPER to pole END.
Move top disk from pole START to pole HELPER.
Move top disk from pole START to pole END.
Move top disk from pole HELPER to pole END.
Press any key to continue . . .</pre>
=={{header|BBC BASIC}}==
{{works with|BBC BASIC for Windows}}
<syntaxhighlight lang="bbcbasic"> DIM Disc$(13),Size%(3)
FOR disc% = 1 TO 13
Disc$(disc%) = STRING$(disc%," ")+STR$disc%+STRING$(disc%," ")
IF disc%>=10 Disc$(disc%) = MID$(Disc$(disc%),2)
Disc$(disc%) = CHR$17+CHR$(128+disc%-(disc%>7))+Disc$(disc%)+CHR$17+CHR$128
NEXT disc%
MODE 3
OFF
ndiscs% = 13
FOR n% = ndiscs% TO 1 STEP -1
PROCput(n%,1)
NEXT
INPUT TAB(0,0) "Press Enter to start" dummy$
PRINT TAB(0,0) SPC(20);
PROChanoi(ndiscs%,1,2,3)
VDU 30
END
DEF PROChanoi(a%,b%,c%,d%)
IF a%=0 ENDPROC
PROChanoi(a%-1,b%,d%,c%)
PROCtake(a%,b%)
PROCput(a%,c%)
PROChanoi(a%-1,d%,c%,b%)
ENDPROC
DEF PROCput(disc%,peg%)
PRINTTAB(13+26*(peg%-1)-disc%,20-Size%(peg%))Disc$(disc%);
Size%(peg%) = Size%(peg%)+1
ENDPROC
DEF PROCtake(disc%,peg%)
Size%(peg%) = Size%(peg%)-1
PRINTTAB(13+26*(peg%-1)-disc%,20-Size%(peg%))STRING$(2*disc%+1," ");
ENDPROC</syntaxhighlight>
=={{header|BCPL}}==
<syntaxhighlight lang="bcpl">get "libhdr"
let start() be move(4, 1, 2, 3)
and move(n, src, via, dest) be if n > 0 do
$( move(n-1, src, dest, via)
writef("Move disk from pole %N to pole %N*N", src, dest);
move(n-1, via, src, dest)
$)</syntaxhighlight>
{{out}}
<pre>Move disk from pole 1 to pole 2
Move disk from pole 1 to pole 3
Move disk from pole 2 to pole 3
Move disk from pole 1 to pole 2
Move disk from pole 3 to pole 1
Move disk from pole 3 to pole 2
Move disk from pole 1 to pole 2
Move disk from pole 1 to pole 3
Move disk from pole 2 to pole 3
Move disk from pole 2 to pole 1
Move disk from pole 3 to pole 1
Move disk from pole 2 to pole 3
Move disk from pole 1 to pole 2
Move disk from pole 1 to pole 3
Move disk from pole 2 to pole 3</pre>
=={{header|Befunge}}==
This is loosely based on the [[Towers_of_Hanoi#Python|Python]] sample. The number of disks is specified by the first integer on the stack (the initial character <tt>4</tt> in the example below). If you want the program to prompt the user for that value, you can replace the <tt>4</tt> with a <tt>&</tt> (the read integer command).
<syntaxhighlight lang="befunge">48*2+1>#v_:!#@_0" ksid evoM">:#,_$:8/:.v
>8v8:<$#<+9-+*2%3\*3/3:,+55.+1%3:$_,#!>#:<
: >/!#^_:0\:8/1-8vv,_$8%:3/1+.>0" gep ot"^
^++3-%3\*2/3:%8\*<>:^:"from peg "0\*8-1<</syntaxhighlight>
{{out}}
<pre>Move disk 1 from peg 1 to peg 2
Move disk 2 from peg 1 to peg 3
Move disk 1 from peg 2 to peg 3
Move disk 3 from peg 1 to peg 2
Move disk 1 from peg 3 to peg 1
Move disk 2 from peg 3 to peg 2
Move disk 1 from peg 1 to peg 2
Move disk 4 from peg 1 to peg 3
Move disk 1 from peg 2 to peg 3
Move disk 2 from peg 2 to peg 1
Move disk 1 from peg 3 to peg 1
Move disk 3 from peg 2 to peg 3
Move disk 1 from peg 1 to peg 2
Move disk 2 from peg 1 to peg 3
Move disk 1 from peg 2 to peg 3</pre>
=={{header|BQN}}==
'''Based on:''' [[APL]]
<syntaxhighlight lang="bqn">Move ← {
𝕩⊑⊸≤0 ? ⟨⟩;
𝕊 n‿from‿to‿via:
l ← 𝕊 ⟨n-1, from, via, to⟩
r ← 𝕊 ⟨n-1, via, to, from⟩
l∾(<from‿to)∾r
}
{"Move disk from pole "∾(•Fmt 𝕨)∾" to pole "∾•Fmt 𝕩}´˘>Move 4‿1‿2‿3</syntaxhighlight>
<syntaxhighlight lang="text">┌─
╵"Move disk from pole 1 to pole 3
Move disk from pole 1 to pole 2
Move disk from pole 3 to pole 2
Move disk from pole 1 to pole 3
Move disk from pole 2 to pole 1
Move disk from pole 2 to pole 3
Move disk from pole 1 to pole 3
Move disk from pole 1 to pole 2
Move disk from pole 3 to pole 2
Move disk from pole 3 to pole 1
Move disk from pole 2 to pole 1
Move disk from pole 3 to pole 2
Move disk from pole 1 to pole 3
Move disk from pole 1 to pole 2
Move disk from pole 3 to pole 2"
┘</syntaxhighlight>
=={{header|Bracmat}}==
<syntaxhighlight lang="bracmat">( ( move
= n from to via
. !arg:(?n,?from,?to,?via)
& ( !n:>0
& move$(!n+-1,!from,!via,!to)
& out$("Move disk from pole " !from " to pole " !to)
& move$(!n+-1,!via,!to,!from)
|
)
)
& move$(4,1,2,3)
);</syntaxhighlight>
{{out}}
<pre>Move disk from pole 1 to pole 3
Move disk from pole 1 to pole 2
Move disk from pole 3 to pole 2
Move disk from pole 1 to pole 3
Move disk from pole 2 to pole 1
Move disk from pole 2 to pole 3
Move disk from pole 1 to pole 3
Move disk from pole 1 to pole 2
Move disk from pole 3 to pole 2
Move disk from pole 3 to pole 1
Move disk from pole 2 to pole 1
Move disk from pole 3 to pole 2
Move disk from pole 1 to pole 3
Move disk from pole 1 to pole 2
Move disk from pole 3 to pole 2</pre>
=={{header|Brainf***}}==
<syntaxhighlight lang="brainfuck">[
This implementation is recursive and uses
a stack, consisting of frames that are 8
bytes long. The layout is as follows:
Byte Description
0 recursion flag
(the program stops if the flag is
zero)
1 the step which is currently
executed
4 means a call to
move(a, c, b, n - 1)
3 means a call to
move(a, b, c, 1)
2 means a call to
move(b, a, c, n - 1)
1 prints the source and dest pile
2 flag to check whether the current
step has already been done or if
it still must be executed
3 the step which will be executed
in the next loop
4 the source pile
5 the helper pile
6 the destination pile
7 the number of disks to move
The first stack frame (0 0 0 0 0 0 0 0)
is used to abort the recursion.
]
>>>>>>>>
These are the parameters for the program
(1 4 1 0 'a 'b 'c 5)
+>++++>+>>
>>>>++++++++[<++++++++++++>-]<
[<<<+>+>+>-]<<<+>++>+++>+++++>
<<<<<<<<
[> while (recurse)
[- if (step gt 0)
>[-]+< todo = 1
[- if (step gt 1)
[- if (step gt 2)
[- if (step gt 3)
>>+++<< next = 3
>-< todo = 0
>>>>>>[>+>+<<-]>[<+>-]> n dup
-
[[-] if (sub(n 1) gt 0)
<+>>>++++> push (1 0 0 4)
copy and push a
<<<<<<<<[>>>>>>>>+>+
<<<<<<<<<-]>>>>>>>>
>[<<<<<<<<<+>>>>>>>>>-]< >
copy and push c
<<<<<<<[>>>>>>>+>+
<<<<<<<<-]>>>>>>>
>[<<<<<<<<+>>>>>>>>-]< >
copy and push b
<<<<<<<<<[>>>>>>>>>+>+
<<<<<<<<<<-]>>>>>>>>>
>[<<<<<<<<<<+>>>>>>>>>>-]< >
copy n and push sub(n 1)
<<<<<<<<[>>>>>>>>+>+
<<<<<<<<<-]>>>>>>>>
>[<<<<<<<<<+>>>>>>>>>-]< -
>>
]
<<<<<<<<
]
>[-< if ((step gt 2) and todo)
>>++<< next = 2
>>>>>>>
+>>>+> push 1 0 0 1 a b c 1
<<<<<<<<[>>>>>>>>+>+
<<<<<<<<<-]>>>>>>>>
>[<<<<<<<<<+>>>>>>>>>-]< > a
<<<<<<<<[>>>>>>>>+>+
<<<<<<<<<-]>>>>>>>>
>[<<<<<<<<<+>>>>>>>>>-]< > b
<<<<<<<<[>>>>>>>>+>+
<<<<<<<<<-]>>>>>>>>
>[<<<<<<<<<+>>>>>>>>>-]< > c
+ >>
>]<
]
>[-< if ((step gt 1) and todo)
>>>>>>[>+>+<<-]>[<+>-]> n dup
-
[[-] if (n sub 1 gt 0)
<+>>>++++> push (1 0 0 4)
copy and push b
<<<<<<<[>>>>>>>+
<<<<<<<-]>>>>>>>
>[<<<<<<<<+>>>>>>>>-]< >
copy and push a
<<<<<<<<<[>>>>>>>>>+
<<<<<<<<<-]>>>>>>>>>
>[<<<<<<<<<<+>>>>>>>>>>-]< >
copy and push c
<<<<<<<<[>>>>>>>>+
<<<<<<<<-]>>>>>>>>
>[<<<<<<<<<+>>>>>>>>>-]< >
copy n and push sub(n 1)
<<<<<<<<[>>>>>>>>+>+
<<<<<<<<<-]>>>>>>>>
>[<<<<<<<<<+>>>>>>>>>-]< -
>>
]
<<<<<<<<
>]<
]
>[-< if ((step gt 0) and todo)
>>>>>>>
>++++[<++++++++>-]<
>>++++++++[<+++++++++>-]<++++
>>++++++++[<++++++++++++>-]<+++++
>>+++++++++[<++++++++++++>-]<+++
<<<
>.+++++++>.++.--.<<.
>>-.+++++.----.<<.
>>>.<---.+++.>+++.+.+.<.<<.
>.>--.+++++.---.++++.
-------.+++.<<.
>>>++.-------.-.<<<.
>+.>>+++++++.---.-----.<<<.
<<<<.>>>>.
>>----.>++++++++.<+++++.<<.
>.>>.---.-----.<<<.
<<.>>++++++++++++++.
>>>[-]<[-]<[-]<[-]
+++++++++++++.---.[-]
<<<<<<<
>]<
>>[<<+>>-]<< step = next
]
return with clear stack frame
<[-]>[-]>[-]>[-]>[-]>[-]>[-]>[-]<<<<<<
<<<<<<<<
>>[<<+>>-]<< step = next
<
]</syntaxhighlight>
=={{header|Bruijn}}==
{{trans|Python}}
<syntaxhighlight lang="bruijn">
:import std/Combinator .
:import std/Number .
:import std/String .
hanoi y [[[[=?2 empty go]]]]
go [(4 --3 2 0) ++ str ++ (4 --3 0 1)] ((+6) - 1 - 0)
str "Move " ++ disk ++ " from " ++ source ++ " to " ++ destination ++ "\n"
disk number→string 3
source number→string 2
destination number→string 1
</syntaxhighlight>
=={{header|C}}==
<syntaxhighlight lang="c">#include <stdio.h>
void move(int n, int from, int via, int to)
{
if (n > 1) {
move(n - 1, from, to, via);
printf("Move disk from pole %d to pole %d\n", from, to);
move(n - 1, via, from, to);
} else {
printf("Move disk from pole %d to pole %d\n", from, to);
}
}
int main()
{
move(4, 1,2,3);
return 0;
}</syntaxhighlight>
Animate it for fun:<syntaxhighlight lang="c">#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
typedef struct { int *x, n; } tower;
tower *new_tower(int cap)
{
tower *t = calloc(1, sizeof(tower) + sizeof(int) * cap);
t->x = (int*)(t + 1);
return t;
}
tower *t[3];
int height;
void text(int y, int i, int d, const char *s)
{
printf("\033[%d;%dH", height - y + 1, (height + 1) * (2 * i + 1) - d);
while (d--) printf("%s", s);
}
void add_disk(int i, int d)
{
t[i]->x[t[i]->n++] = d;
text(t[i]->n, i, d, "==");
usleep(100000);
fflush(stdout);
}
int remove_disk(int i)
{
int d = t[i]->x[--t[i]->n];
text(t[i]->n + 1, i, d, " ");
return d;
}
void move(int n, int from, int to, int via)
{
if (!n) return;
move(n - 1, from, via, to);
add_disk(to, remove_disk(from));
move(n - 1, via, to, from);
}
int main(int c, char *v[])
{
puts("\033[H\033[J");
if (c <= 1 || (height = atoi(v[1])) <= 0)
height = 8;
for (c = 0; c < 3; c++) t[c] = new_tower(height);
for (c = height; c; c--) add_disk(0, c);
move(height, 0, 2, 1);
text(1, 0, 1, "\n");
return 0;
}</syntaxhighlight>
=={{header|C sharp|C#}}==
<syntaxhighlight lang="csharp">public void move(int n, int from, int to, int via) {
if (n == 1) {
System.Console.WriteLine("Move disk from pole " + from + " to pole " + to);
} else {
move(n - 1, from, via, to);
move(1, from, to, via);
move(n - 1, via, to, from);
}
}</syntaxhighlight>
=={{header|C++}}==
{{works with|g++}}
<syntaxhighlight lang="cpp">void move(int n, int from, int to, int via) {
if (n == 1) {
std::cout << "Move disk from pole " << from << " to pole " << to << std::endl;
} else {
move(n - 1, from, via, to);
move(1, from, to, via);
move(n - 1, via, to, from);
}
}</syntaxhighlight>
==={{header|Chipmunk Basic}}===
{{works with|Chipmunk Basic|3.6.4}}
{{trans|FreeBASIC}}
<syntaxhighlight lang="qbasic">100 cls
110 print "Three disks" : print
120 hanoi(3,1,2,3)
130 print chr$(10)"Four disks" chr$(10)
140 hanoi(4,1,2,3)
150 print : print "Towers of Hanoi puzzle completed!"
160 end
170 sub hanoi(n,desde,hasta,via)
180 if n > 0 then
190 hanoi(n-1,desde,via,hasta)
200 print "Move disk " n "from pole " desde "to pole " hasta
210 hanoi(n-1,via,hasta,desde)
220 endif
230 end sub</syntaxhighlight>
=={{header|Clojure}}==
===Side-Effecting Solution===
<syntaxhighlight lang="lisp">(defn towers-of-hanoi [n from to via]
(when (pos? n)
(towers-of-hanoi (dec n) from via to)
(printf "Move from %s to %s\n" from to)
(recur (dec n) via to from)))</syntaxhighlight>
===Lazy Solution===
<syntaxhighlight lang="lisp">(defn towers-of-hanoi [n from to via]
(when (pos? n)
(lazy-cat (towers-of-hanoi (dec n) from via to)
(cons [from '-> to]
(towers-of-hanoi (dec n) via to from)))))</syntaxhighlight>
=={{header|CLU}}==
<syntaxhighlight lang="clu">move = proc (n, from, via, to: int)
po: stream := stream$primary_output()
if n > 0 then
move(n-1, from, to, via)
stream$putl(po, "Move disk from pole "
|| int$unparse(from)
|| " to pole "
|| int$unparse(to))
move(n-1, via, from, to)
end
end move
start_up = proc ()
move(4, 1, 2, 3)
end start_up</syntaxhighlight>
{{out}}
<pre>Move disk from pole 1 to pole 2
Move disk from pole 1 to pole 3
Move disk from pole 2 to pole 3
Move disk from pole 1 to pole 2
Move disk from pole 3 to pole 1
Move disk from pole 3 to pole 2
Move disk from pole 1 to pole 2
Move disk from pole 1 to pole 3
Move disk from pole 2 to pole 3
Move disk from pole 2 to pole 1
Move disk from pole 3 to pole 1
Move disk from pole 2 to pole 3
Move disk from pole 1 to pole 2
Move disk from pole 1 to pole 3
Move disk from pole 2 to pole 3</pre>
=={{header|COBOL}}==
{{trans|C}}
{{works with|OpenCOBOL|2.0}}
<syntaxhighlight lang="cobol"> >>SOURCE FREE
IDENTIFICATION DIVISION.
PROGRAM-ID. towers-of-hanoi.
PROCEDURE DIVISION.
CALL "move-disk" USING 4, 1, 2, 3
.
END PROGRAM towers-of-hanoi.
IDENTIFICATION DIVISION.
PROGRAM-ID. move-disk RECURSIVE.
DATA DIVISION.
LINKAGE SECTION.
01 n PIC 9 USAGE COMP.
01 from-pole PIC 9 USAGE COMP.
01 to-pole PIC 9 USAGE COMP.
01 via-pole PIC 9 USAGE COMP.
PROCEDURE DIVISION USING n, from-pole, to-pole, via-pole.
IF n > 0
SUBTRACT 1 FROM n
CALL "move-disk" USING CONTENT n, from-pole, via-pole, to-pole
DISPLAY "Move disk from pole " from-pole " to pole " to-pole
CALL "move-disk" USING CONTENT n, via-pole, to-pole, from-pole
END-IF
.
END PROGRAM move-disk.</syntaxhighlight>
{{ Number of disks also }}
<syntaxhighlight lang="cobol">
IDENTIFICATION DIVISION.
PROGRAM-ID. towers-of-hanoi.
PROCEDURE DIVISION.
CALL "move-disk" USING 4, 1, 2, 3
.
END PROGRAM towers-of-hanoi.
IDENTIFICATION DIVISION.
PROGRAM-ID. move-disk RECURSIVE.
DATA DIVISION.
LINKAGE SECTION.
01 n PIC 9 USAGE COMP.
01 from-pole PIC 9 USAGE COMP.
01 to-pole PIC 9 USAGE COMP.
01 via-pole PIC 9 USAGE COMP.
PROCEDURE DIVISION USING n, from-pole, to-pole, via-pole.
IF n > 0
SUBTRACT 1 FROM n
CALL "move-disk" USING CONTENT n, from-pole, via-pole, to-pole
ADD 1 TO n
DISPLAY "Move disk number "n " from pole " from-pole " to pole " to-pole
SUBTRACT 1 FROM n
CALL "move-disk" USING CONTENT n, via-pole, to-pole, from-pole
END-IF
.
END PROGRAM move-disk.
</syntaxhighlight>
=== ANSI-74 solution ===
Early versions of COBOL did not have recursion. There are no locally-scoped variables and the call of a procedure does not have to use a stack to save return state. Recursion would cause undefined results. It is therefore necessary to use an iterative algorithm. This solution is an adaptation of [http://hanoitower.mkolar.org/algo.html Kolar's Hanoi Tower algorithm no. 1].
{{works with|CIS COBOL|4.2}}{{works with|GnuCOBOL|3.0-rc1.0}}
<syntaxhighlight lang="cobol"> IDENTIFICATION DIVISION.
PROGRAM-ID. ITERATIVE-TOWERS-OF-HANOI.
AUTHOR. SOREN ROUG.
DATE-WRITTEN. 2019-06-28.
ENVIRONMENT DIVISION.
CONFIGURATION SECTION.
SOURCE-COMPUTER. LINUX.
OBJECT-COMPUTER. KAYPRO4.
INPUT-OUTPUT SECTION.
FILE-CONTROL.
DATA DIVISION.
WORKING-STORAGE SECTION.
77 NUM-DISKS PIC 9 VALUE 4.
77 N1 PIC 9 COMP.
77 N2 PIC 9 COMP.
77 FROM-POLE PIC 9 COMP.
77 TO-POLE PIC 9 COMP.
77 VIA-POLE PIC 9 COMP.
77 FP-TMP PIC 9 COMP.
77 TO-TMP PIC 9 COMP.
77 P-TMP PIC 9 COMP.
77 TMP-P PIC 9 COMP.
77 I PIC 9 COMP.
77 DIV PIC 9 COMP.
01 STACKNUMS.
05 NUMSET OCCURS 3 TIMES.
10 DNUM PIC 9 COMP.
01 GAMESET.
05 POLES OCCURS 3 TIMES.
10 STACK OCCURS 10 TIMES.
15 POLE PIC 9 USAGE COMP.
PROCEDURE DIVISION.
HANOI.
DISPLAY "TOWERS OF HANOI PUZZLE WITH ", NUM-DISKS, " DISKS.".
ADD NUM-DISKS, 1 GIVING N1.
ADD NUM-DISKS, 2 GIVING N2.
MOVE 1 TO DNUM (1).
MOVE N1 TO DNUM (2), DNUM (3).
MOVE N1 TO POLE (1, N1), POLE (2, N1), POLE (3, N1).
MOVE 1 TO POLE (1, N2).
MOVE 2 TO POLE (2, N2).
MOVE 3 TO POLE (3, N2).
MOVE 1 TO I.
PERFORM INIT-PUZZLE UNTIL I = N1.
MOVE 1 TO FROM-POLE.
DIVIDE 2 INTO NUM-DISKS GIVING DIV.
MULTIPLY 2 BY DIV.
IF DIV NOT = NUM-DISKS PERFORM INITODD ELSE PERFORM INITEVEN.
PERFORM MOVE-DISK UNTIL DNUM (3) NOT > 1.
DISPLAY "TOWERS OF HANOI PUZZLE COMPLETED!".
STOP RUN.
INIT-PUZZLE.
MOVE I TO POLE (1, I).
MOVE 0 TO POLE (2, I), POLE (3, I).
ADD 1 TO I.
INITEVEN.
MOVE 2 TO TO-POLE.
MOVE 3 TO VIA-POLE.
INITODD.
MOVE 3 TO TO-POLE.
MOVE 2 TO VIA-POLE.
MOVE-DISK.
MOVE DNUM (FROM-POLE) TO FP-TMP.
MOVE POLE (FROM-POLE, FP-TMP) TO I.
DISPLAY "MOVE DISK FROM ", POLE (FROM-POLE, N2),
" TO ", POLE (TO-POLE, N2).
ADD 1 TO DNUM (FROM-POLE).
MOVE VIA-POLE TO TMP-P.
SUBTRACT 1 FROM DNUM (TO-POLE).
MOVE DNUM (TO-POLE) TO TO-TMP.
MOVE I TO POLE (TO-POLE, TO-TMP).
DIVIDE 2 INTO I GIVING DIV.
MULTIPLY 2 BY DIV.
IF I NOT = DIV PERFORM MOVE-TO-VIA ELSE
PERFORM MOVE-FROM-VIA.
MOVE-TO-VIA.
MOVE TO-POLE TO VIA-POLE.
MOVE DNUM (FROM-POLE) TO FP-TMP.
MOVE DNUM (TMP-P) TO P-TMP.
IF POLE (FROM-POLE, FP-TMP) > POLE (TMP-P, P-TMP)
PERFORM MOVE-FROM-TO
ELSE MOVE TMP-P TO TO-POLE.
MOVE-FROM-TO.
MOVE FROM-POLE TO TO-POLE.
MOVE TMP-P TO FROM-POLE.
MOVE DNUM (FROM-POLE) TO FP-TMP.
MOVE DNUM (TMP-P) TO P-TMP.
MOVE-FROM-VIA.
MOVE FROM-POLE TO VIA-POLE.
MOVE TMP-P TO FROM-POLE.
</syntaxhighlight>
=={{header|CoffeeScript}}==
<syntaxhighlight lang="coffeescript">hanoi = (ndisks, start_peg=1, end_peg=3) ->
if ndisks
staging_peg = 1 + 2 + 3 - start_peg - end_peg
hanoi(ndisks-1, start_peg, staging_peg)
console.log "Move disk #{ndisks} from peg #{start_peg} to #{end_peg}"
hanoi(ndisks-1, staging_peg, end_peg)
hanoi(4)</syntaxhighlight>
=={{header|Common Lisp}}==
<syntaxhighlight lang="lisp">(defun move (n from to via)
(cond ((= n 1)
(format t "Move from ~A to ~A.~%" from to))
(t
(move (- n 1) from via to)
(format t "Move from ~A to ~A.~%" from to)
(move (- n 1) via to from))))</syntaxhighlight>
=={{header|D}}==
===Recursive Version===
<syntaxhighlight lang="d">import std.stdio;
void hanoi(in int n, in char from, in char to, in char via) {
if (n > 0) {
hanoi(n - 1, from, via, to);
writefln("Move disk %d from %s to %s", n, from, to);
hanoi(n - 1, via, to, from);
}
}
void main() {
hanoi(3, 'L', 'M', 'R');
}</syntaxhighlight>
{{out}}
<pre>Move disk 1 from L to M
Move disk 2 from L to R
Move disk 1 from M to R
Move disk 3 from L to M
Move disk 1 from R to L
Move disk 2 from R to M
Move disk 1 from L to M</pre>
===Fast Iterative Version===
See: [http://hanoitower.mkolar.org/shortestTHalgo.html The shortest and "mysterious" TH algorithm]
<syntaxhighlight lang="d">// Code found and then improved by Glenn C. Rhoads,
// then some more by M. Kolar (2000).
void main(in string[] args) {
import core.stdc.stdio, std.conv, std.typetuple;
immutable size_t n = (args.length > 1) ? args[1].to!size_t : 3;
size_t[3] p = [(1 << n) - 1, 0, 0];
// Show the start configuration of the pegs.
'|'.putchar;
foreach_reverse (immutable i; 1 .. n + 1)
printf(" %d", i);
"\n|\n|".puts;
foreach (immutable size_t x; 1 .. (1 << n)) {
{
immutable size_t i1 = x & (x - 1);
immutable size_t fr = (i1 + i1 / 3) & 3;
immutable size_t i2 = (x | (x - 1)) + 1;
immutable size_t to = (i2 + i2 / 3) & 3;
size_t j = 1;
for (size_t w = x; !(w & 1); w >>= 1, j <<= 1) {}
// Now j is not the number of the disk to move,
// it contains the single bit to be moved:
p[fr] &= ~j;
p[to] |= j;
}
// Show the current configuration of pegs.
foreach (immutable size_t k; TypeTuple!(0, 1, 2)) {
"\n|".printf;
size_t j = 1 << n;
foreach_reverse (immutable size_t w; 1 .. n + 1) {
j >>= 1;
if (j & p[k])
printf(" %zd", w);
}
}
'\n'.putchar;
}
}</syntaxhighlight>
{{out}}
<pre>| 3 2 1
|
|
| 3 2
|
| 1
| 3
| 2
| 1
| 3
| 2 1
|
|
| 2 1
| 3
| 1
| 2
| 3
| 1
|
| 3 2
|
|
| 3 2 1
</pre>
=={{header|Dart}}==
<syntaxhighlight lang="dart">main() {
moveit(from,to) {
print("move ${from} ---> ${to}");
}
hanoi(height,toPole,fromPole,usePole) {
if (height>0) {
hanoi(height-1,usePole,fromPole,toPole);
moveit(fromPole,toPole);
hanoi(height-1,toPole,usePole,fromPole);
}
}
hanoi(3,3,1,2);
}</syntaxhighlight>
The same as above, with optional static type annotations and styled according to http://www.dartlang.org/articles/style-guide/
<syntaxhighlight lang="dart">main() {
String say(String from, String to) => "$from ---> $to";
hanoi(int height, int toPole, int fromPole, int usePole) {
if (height > 0) {
hanoi(height - 1, usePole, fromPole, toPole);
print(say(fromPole.toString(), toPole.toString()));
hanoi(height - 1, toPole, usePole, fromPole);
}
}
hanoi(3, 3, 1, 2);
}</syntaxhighlight>
{{out}}
<pre>move 1 ---> 3
move 1 ---> 2
move 3 ---> 2
move 1 ---> 3
move 2 ---> 1
move 2 ---> 3
move 1 ---> 3
</pre>
=={{header|Dc}}==
From [http://se.aminet.net/pub/OpenBSD/src/regress/usr.bin/dc/t20.in Here]
<pre>
[ # move(from, to)
n # print from
[ --> ]n # print " --> "
p # print to\n
sw # p doesn't pop, so get rid of the value
]sm
[ # init(n)
sw # tuck n away temporarily
9 # sentinel as bottom of stack
lw # bring n back
1 # "from" tower's label
3 # "to" tower's label
0 # processed marker
]si
[ # Move()
lt # push to
lf # push from
lmx # call move(from, to)
]sM
[ # code block <d>
ln # push n
lf # push from
lt # push to
1 # push processed marker 1
ln # push n
1 # push 1
- # n - 1
lf # push from
ll # push left
0 # push processed marker 0
]sd
[ # code block <e>
ln # push n
1 # push 1
- # n - 1
ll # push left
lt # push to
0 # push processed marker 0
]se
[ # code block <x>
ln 1 =M
ln 1 !=d
]sx
[ # code block <y>
lMx
lex
]sy
[ # quit()
q # exit the program
]sq
[ # run()
d 9 =q # if stack empty, quit()
sp # processed
st # to
sf # from
sn # n
6 #
lf #
- #
lt #
- # 6 - from - to
sl #
lp 0 =x #
lp 0 !=y #
lrx # loop
]sr
5lix # init(n)
lrx # run()
</pre>
=={{header|Delphi}}==
See [https://rosettacode.org/wiki/Towers_of_Hanoi#Pascal Pascal].
=={{header|Draco}}==
<syntaxhighlight lang="draco">proc move(byte n, src, via, dest) void:
if n>0 then
move(n-1, src, dest, via);
writeln("Move disk from pole ",src," to pole ",dest);
move(n-1, via, src, dest)
fi
corp
proc nonrec main() void:
move(4, 1, 2, 3)
corp</syntaxhighlight>
{{out}}
<pre>Move disk from pole 1 to pole 2
Move disk from pole 1 to pole 3
Move disk from pole 2 to pole 3
Move disk from pole 1 to pole 2
Move disk from pole 3 to pole 1
Move disk from pole 3 to pole 2
Move disk from pole 1 to pole 2
Move disk from pole 1 to pole 3
Move disk from pole 2 to pole 3
Move disk from pole 2 to pole 1
Move disk from pole 3 to pole 1
Move disk from pole 2 to pole 3
Move disk from pole 1 to pole 2
Move disk from pole 1 to pole 3
Move disk from pole 2 to pole 3</pre>
=={{header|Dyalect}}==
{{trans|Swift}}
<syntaxhighlight lang="dyalect">func hanoi(n, a, b, c) {
if n > 0 {
hanoi(n - 1, a, c, b)
print("Move disk from \(a) to \(c)")
hanoi(n - 1, b, a, c)
}
}
hanoi(4, "A", "B", "C")</syntaxhighlight>
{{out}}
<pre>Move disk from A to B
Move disk from A to C
Move disk from B to C
Move disk from A to B
Move disk from C to A
Move disk from C to B
Move disk from A to B
Move disk from A to C
Move disk from B to C
Move disk from B to A
Move disk from C to A
Move disk from B to C
Move disk from A to B
Move disk from A to C
Move disk from B to C</pre>
=={{header|E}}==
<syntaxhighlight lang="e">def move(out, n, fromPeg, toPeg, viaPeg) {
if (n.aboveZero()) {
move(out, n.previous(), fromPeg, viaPeg, toPeg)
out.println(`Move disk $n from $fromPeg to $toPeg.`)
move(out, n.previous(), viaPeg, toPeg, fromPeg)
}
}
move(stdout, 4, def left {}, def right {}, def middle {})</syntaxhighlight>
=={{header|EasyLang}}==
<syntaxhighlight lang="text">
proc hanoi n src dst aux . .
if n >= 1
hanoi n - 1 src aux dst
print "Move " & src & " to " & dst
hanoi n - 1 aux dst src
.
.
hanoi 5 1 2 3
</syntaxhighlight>
=={{header|EDSAC order code}}==
The Wikipedia article on EDSAC says "recursive calls were forbidden", and this is true if the standard "Wheeler jump" is used. In the Wheeler jump, the caller (in effect) passes the return address to the subroutine, which uses that address to manufacture a "link order", i.e. a jump back to the caller. This link order is normally stored at a fixed location in the subroutine, so if the subroutine were to call itself then the original link order would be overwritten and lost. However, it is easy enough to make a subroutine save its link orders in a stack, so that it can be called recursively, as the Rosetta Code task requires.
The program has a maximum of 9 discs, so as to simplify the printout of the disc numbers. Discs are numbered 1, 2, 3, ... in increasing order of size. The program could be speeded up by shortening the messages, which at present take up most of the runtime.
<syntaxhighlight lang="edsac">
[Towers of Hanoi task for Rosetta Code.]
[EDSAC program, Initial Orders 2.]
T100K [load program at location 100 (arbitrary)]
GK
[Number of discs, in the address field]
[0] P3F [<--- edit here, value 1..9]
[Letters to represent the rods]
[1] LF [left]
[2] CF [centre]
[3] RF [right]
[Main routine. Enter with acc = 0]
[4] T1F [1F := 0]
[5] A5@ [initialize recursive subroutine]
G104@
A@ [number of discs]
T1F [pass to subroutines]
A1@ [source rod]
T4F [pass to subroutines]
A3@ [target rod]
T5F [pass to subroutines]
[13] A13@ [call subroutine to write header ]
G18@
[15] A15@ [call recursive subroutine to write moves ]
G104@
ZF [stop]
[Subroutine to write a header]
[Input: 1F = number of discs (in the address field)]
[4F = letter for starting rod]
[5F = letter for ending rod]
[Output: None. 1F, 4F, 5F must be preserved.]
[18] A3F [plant return link as usual]
T35@
A1F [number of discs]
L512F [shift 11 left to make output char]
T39@ [plant in message]
A4F [starting rod]
T53@ [plant in message]
A5F [ending rod]
T58@ [plant in message]
A36@ [O order for first char of message]
E30@ [skip next order (code for 'O' is positive)]
[29] A37@ [restore acc after test below]
[30] U31@ [plant order to write next character]
[31] OF [(planted) write next character]
A2F [inc address in previous order]
S37@ [finished yet?]
G29@ [if not, loop back]
[35] ZF [(planted) exit with acc = 0]
[36] O38@ [O order for start of message]
[37] O61@ [O order for exclusive end of message]
[38] #F
[39] PFK2048F!FDFIFSFCFSF!FFFRFOFMF!F
[53] PF!FTFOF!F
[58] PF@F&F
[61]
[Subroutine to write a move of one disc.]
[Input: 1F = disc number 1..9 (in the address field)]
[4F = letter for source rod]
[5F = letter for target rod]
[Output: None. 1F, 4F, 5F must be preserved.]
[Condensed to save space; very similar to previous subroutine.]
[61] A3FT78@A1FL512FT88@ A4FT96@A5FT101@A79@E73@
[72] A80@
[73] U74@
[74] OFA2FS80@G72@
[78] ZF [(planted) exit with acc = 0]
[79] O81@
[80] O104@
[81] K2048FMFOFVFEF!F#F
[88] PFK2048F!FFFRFOFMF!F
[96] PF!FTFOF!F
[101] PF@F&F
[104]
[Recursive subroutine to move discs 1..n, where 1 <= n <= 9.]
[Call with n = 0 to initialize.]
[Input: 1F = n (in the address field)]
[4F = letter for source rod]
[5F = letter for target rod]
[Output: None. 1F, 4F, 5F must be preserved.]
[104] A3F [plant link as usual ]
T167@
[The link will be saved in a stack if recursive calls are required.]
S1F [load -n]
G115@ [jump if n > 0]
[Here if n = 0. Initialize; no recursive calls.]
A169@ [initialize push order to start of stack]
T122@
A1@ [find total of the codes for the rod letters]
A2@
A3@
T168@ [store for future use]
E167@ [jump to link]
[Here with acc = -n in address field]
[115] A2F [add 1]
G120@ [jump if n > 1]
[Here if n = 1. Just write the move; no recursive calls.]
[117] A117@ [call write subroutine]
G61@
E167@ [jump to link]
[Here if n > 1. Recursive calls are required.]
[120] TF [clear acc]
A167@ [load link order]
[122] TF [(planted) push link order onto stack]
A122@ [inc address in previous order]
A2F
T122@
[First recursive call. Modify parameters 1F and 5F; 4F stays the same]
A1F [load n]
S2F [make n - 1]
T1F [pass as parameter]
A168@ [get 3rd rod, neither source nor target]
S4F
S5F
T5F
[133] A133@ [recursive call]
G104@
[Returned, restore parameters]
A1F
A2F
T1F
A168@
S4F
S5F
T5F
[Write move of largest disc]
[142] A142@
G61@
[Second recursive call. Modify parameters 1F and 4F; 5F stays the same]
[Condensed to save space; very similar to first recursice call.]
A1FS2FT1FA168@S4FS5FT4F
[151] A151@G104@A1FA2FT1FA168@S4FS5FT4F
[Pop return link off stack]
A122@ [dec address in push order]
S2F
U122@
A170@ [make A order with same address]
T165@ [plant in code]
[165] AF [(planted) pop return link from stack]
T167@ [plant in code]
[167] ZF [(planted) return to caller]
[Constants]
[168] PF [(planted) sum of letters for rods]
[169] T171@ [T order for start of stack]
[170] MF [add to T order to make A order, same address]
[Stack: placed at end of program, grows into free space.]
[171]
E4Z [define entry point]
PF [acc = 0 on entry]
[end]
</syntaxhighlight>
{{out}}
<pre>
3 DISCS FROM L TO R
MOVE 1 FROM L TO R
MOVE 2 FROM L TO C
MOVE 1 FROM R TO C
MOVE 3 FROM L TO R
MOVE 1 FROM C TO L
MOVE 2 FROM C TO R
MOVE 1 FROM L TO R
</pre>
=={{header|Eiffel}}==
<syntaxhighlight lang="eiffel">class
APPLICATION
create
make
feature {NONE} -- Initialization
make
do
move (4, "A", "B", "C")
end
feature -- Towers of Hanoi
move (n: INTEGER; frm, to, via: STRING)
require
n > 0
do
if n = 1 then
print ("Move disk from pole " + frm + " to pole " + to + "%N")
else
move (n - 1, frm, via, to)
move (1, frm, to, via)
move (n - 1, via, to, frm)
end
end
end</syntaxhighlight>
=={{header|Ela}}==
{{trans|Haskell}}
<syntaxhighlight lang="ela">open monad io
:::IO
//Functional approach
hanoi 0 _ _ _ = []
hanoi n a b c = hanoi (n - 1) a c b ++ [(a,b)] ++ hanoi (n - 1) c b a
hanoiIO n = mapM_ f $ hanoi n 1 2 3 where
f (x,y) = putStrLn $ "Move " ++ show x ++ " to " ++ show y
//Imperative approach using IO monad
hanoiM n = hanoiM' n 1 2 3 where
hanoiM' 0 _ _ _ = return ()
hanoiM' n a b c = do
hanoiM' (n - 1) a c b
putStrLn $ "Move " ++ show a ++ " to " ++ show b
hanoiM' (n - 1) c b a</syntaxhighlight>
=={{header|Elena}}==
ELENA 4.x :
<syntaxhighlight lang="elena">move = (n,from,to,via)
{
if (n == 1)
{
console.printLine("Move disk from pole ",from," to pole ",to)
}
else
{
move(n-1,from,via,to);
move(1,from,to,via);
move(n-1,via,to,from)
}
};</syntaxhighlight>
=={{header|Elixir}}==
<syntaxhighlight lang="elixir">defmodule RC do
def hanoi(n) when 0<n and n<10, do: hanoi(n, 1, 2, 3)
defp hanoi(1, f, _, t), do: move(f, t)
defp hanoi(n, f, u, t) do
hanoi(n-1, f, t, u)
move(f, t)
hanoi(n-1, u, f, t)
end
defp move(f, t), do: IO.puts "Move disk from #{f} to #{t}"
end
RC.hanoi(3)</syntaxhighlight>
{{out}}
<pre>
Move disk from 1 to 3
Move disk from 1 to 2
Move disk from 3 to 2
Move disk from 1 to 3
Move disk from 2 to 1
Move disk from 2 to 3
Move disk from 1 to 3
</pre>
=={{header|Emacs Lisp}}==
{{Trans|Common Lisp}}
<syntaxhighlight lang="lisp">(defun move (n from to via)
(if (= n 1)
(message "Move from %S to %S" from to)
(move (- n 1) from via to)
(message "Move from %S to %S" from to)
(move (- n 1) via to from)))</syntaxhighlight>
=={{header|EMal}}==
{{trans|C#}}
<syntaxhighlight lang="emal">
fun move = void by int n, int from, int to, int via
if n == 1
writeLine("Move disk from pole " + from + " to pole " + to)
return
end
move(n - 1, from, via, to)
move(1, from, to, via)
move(n - 1, via, to, from)
end
move(3, 1, 2, 3)
</syntaxhighlight>
{{out}}
<pre>
Move disk from pole 1 to pole 2
Move disk from pole 1 to pole 3
Move disk from pole 2 to pole 3
Move disk from pole 1 to pole 2
Move disk from pole 3 to pole 1
Move disk from pole 3 to pole 2
Move disk from pole 1 to pole 2
</pre>
=={{header|Erlang}}==
<syntaxhighlight lang="erlang">move(1, F, T, _V) ->
io:format("Move from ~p to ~p~n", [F, T]);
move(N, F, T, V) ->
move(N-1, F, V, T),
move(1 , F, T, V),
move(N-1, V, T, F).</syntaxhighlight>
=={{header|ERRE}}==
<syntaxhighlight lang="erre">
!-----------------------------------------------------------
! HANOI.R : solve tower of Hanoi puzzle using a recursive
! modified algorithm.
!-----------------------------------------------------------
PROGRAM HANOI
!$INTEGER
!VAR I,J,MOSSE,NUMBER
PROCEDURE PRINTMOVE
LOCAL SOURCE$,DEST$
MOSSE=MOSSE+1
CASE I OF
1-> SOURCE$="Left" END ->
2-> SOURCE$="Center" END ->
3-> SOURCE$="Right" END ->
END CASE
CASE J OF
1-> DEST$="Left" END ->
2-> DEST$="Center" END ->
3-> DEST$="Right" END ->
END CASE
PRINT("I move a disk from ";SOURCE$;" to ";DEST$)
END PROCEDURE
PROCEDURE MOVE
IF NUMBER<>0 THEN
NUMBER=NUMBER-1
J=6-I-J
MOVE
J=6-I-J
PRINTMOVE
I=6-I-J
MOVE
I=6-I-J
NUMBER=NUMBER+1
END IF
END PROCEDURE
BEGIN
MAXNUM=12
MOSSE=0
PRINT(CHR$(12);TAB(25);"--- TOWERS OF HANOI ---")
REPEAT
PRINT("Number of disks ";)
INPUT(NUMBER)
UNTIL NUMBER>1 AND NUMBER<=MAXNUM
PRINT
PRINT("For ";NUMBER;"disks the total number of moves is";2^NUMBER-1)
I=1 ! number of source pole
J=3 ! number of destination pole
MOVE
END PROGRAM
</syntaxhighlight>
{{out}}
<pre>
--- TOWER OF HANOI ---
Number of disks ? 3
For 3 disks the total number of moves is 7
I move a disk from Left to Right
I move a disk from Left to Center
I move a disk from Right to Center
I move a disk from Left to Right
I move a disk from Center to Left
I move a disk from Center to Right
I move a disk from Left to Right
</pre>
=={{header|Excel}}==
===LAMBDA===
With the names HANOI and SHOWHANOI bound to the following lambdas in the Excel worksheet Name Manager:
(See [https://www.microsoft.com/en-us/research/blog/lambda-the-ultimatae-excel-worksheet-function/ LAMBDA: The ultimate Excel worksheet function])
{{Works with| Office 365 Betas 2021}}
<syntaxhighlight lang="lisp">SHOWHANOI
=LAMBDA(n,
FILTERP(
LAMBDA(x, "" <> x)
)(
HANOI(n)("left")("right")("mid")
)
)
HANOI
=LAMBDA(n,
LAMBDA(l,
LAMBDA(r,
LAMBDA(m,
IF(0 = n,
"",
LET(
next, n - 1,
APPEND(
APPEND(
HANOI(next)(l)(m)(r)
)(
CONCAT(l, " -> ", r)
)
)(
HANOI(next)(m)(r)(l)
)
)
)
)
)
)
)</syntaxhighlight>
And assuming that these generic lambdas are also bound to the following names in Name Manager:
<syntaxhighlight lang="lisp">APPEND
=LAMBDA(xs,
LAMBDA(ys,
LET(
nx, ROWS(xs),
rowIndexes, SEQUENCE(nx + ROWS(ys)),
colIndexes, SEQUENCE(
1,
MAX(COLUMNS(xs), COLUMNS(ys))
),
IF(
rowIndexes <= nx,
INDEX(xs, rowIndexes, colIndexes),
INDEX(ys, rowIndexes - nx, colIndexes)
)
)
)
)
FILTERP
=LAMBDA(p,
LAMBDA(xs,
FILTER(xs, p(xs))
)
)</syntaxhighlight>
In the output below, the expression in B2 defines an array of strings which additionally populate the following cells.
{{Out}}
{| class="wikitable"
|-
|||style="text-align:right; font-family:serif; font-style:italic; font-size:120%;"|fx
! colspan="2" style="text-align:left; vertical-align: bottom; font-family:Arial, Helvetica, sans-serif !important;"|=SHOWHANOI(A2)
|- style="text-align:center; font-family:Arial, Helvetica, sans-serif !important; background-color:#000000; color:#ffffff;"
|
| A
| B
|- style="text-align:right;"
| style="text-align:center; font-family:Arial, Helvetica, sans-serif !important; background-color:#000000; color:#ffffff" | 1
| style="text-align:right; font-weight:bold" | Disks
| style="font-weight:bold" | Steps
|- style="text-align:right;"
| style="text-align:center; font-family:Arial, Helvetica, sans-serif !important; background-color:#000000; color:#ffffff" | 2
| style="text-align:right; font-weight:bold" | 3
| style="background-color:#cbcefb;" | left -> right
|- style="text-align:right;"
| style="text-align:center; font-family:Arial, Helvetica, sans-serif !important; background-color:#000000; color:#ffffff" | 3
| style="text-align:right; font-weight:bold" |
| left -> mid
|- style="text-align:right;"
| style="text-align:center; font-family:Arial, Helvetica, sans-serif !important; background-color:#000000; color:#ffffff" | 4
| style="text-align:right; font-weight:bold" |
| right -> mid
|- style="text-align:right;"
| style="text-align:center; font-family:Arial, Helvetica, sans-serif !important; background-color:#000000; color:#ffffff" | 5
| style="text-align:right; font-weight:bold" |
| left -> right
|- style="text-align:right;"
| style="text-align:center; font-family:Arial, Helvetica, sans-serif !important; background-color:#000000; color:#ffffff" | 6
| style="text-align:right; font-weight:bold" |
| mid -> left
|- style="text-align:right;"
| style="text-align:center; font-family:Arial, Helvetica, sans-serif !important; background-color:#000000; color:#ffffff" | 7
| style="text-align:right; font-weight:bold" |
| mid -> right
|- style="text-align:right;"
| style="text-align:center; font-family:Arial, Helvetica, sans-serif !important; background-color:#000000; color:#ffffff" | 8
| style="text-align:right; font-weight:bold" |
| left -> right
|}
=={{header|Ezhil}}==
<syntaxhighlight lang="python">
# (C) 2013 Ezhil Language Project
# Tower of Hanoi – recursive solution
நிரல்பாகம் ஹோனாய்(வட்டுகள், முதல்அச்சு, இறுதிஅச்சு,வட்டு)
@(வட்டுகள் == 1 ) ஆனால்
பதிப்பி “வட்டு ” + str(வட்டு) + “ஐ \t (” + str(முதல்அச்சு) + “ —> ” + str(இறுதிஅச்சு)+ “) அச்சிற்கு நகர்த்துக.”
இல்லை
@( ["இ", "அ", "ஆ"] இல் அச்சு ) ஒவ்வொன்றாக
@( (முதல்அச்சு != அச்சு) && (இறுதிஅச்சு != அச்சு) ) ஆனால்
நடு = அச்சு
முடி
முடி
# solve problem for n-1 again between src and temp pegs
ஹோனாய்(வட்டுகள்-1, முதல்அச்சு,நடு,வட்டுகள்-1)
# move largest disk from src to destination
ஹோனாய்(1, முதல்அச்சு, இறுதிஅச்சு,வட்டுகள்)
# solve problem for n-1 again between different pegs
ஹோனாய்(வட்டுகள்-1, நடு, இறுதிஅச்சு,வட்டுகள்-1)
முடி
முடி
ஹோனாய்(4,”அ”,”ஆ”,0)
</syntaxhighlight>
=={{header|F_Sharp|F#}}==
<syntaxhighlight lang="fsharp">#light
let rec hanoi num start finish =
match num with
| 0 -> [ ]
| _ -> let temp = (6 - start - finish)
(hanoi (num-1) start temp) @ [ start, finish ] @ (hanoi (num-1) temp finish)
[<EntryPoint>]
let main args =
(hanoi 4 1 2) |> List.iter (fun pair -> match pair with
| a, b -> printf "Move disc from %A to %A\n" a b)
0</syntaxhighlight>
=={{header|Factor}}==
<syntaxhighlight lang="factor">USING: formatting kernel locals math ;
IN: rosettacode.hanoi
: move ( from to -- )
"%d->%d\n" printf ;
:: hanoi ( n from to other -- )
n 0 > [
n 1 - from other to hanoi
from to move
n 1 - other to from hanoi
] when ;</syntaxhighlight>
In the REPL:
<pre>( scratchpad ) 3 1 3 2 hanoi
1->3
1->2
3->2
1->3
2->1
2->3
1->3</pre>
=={{header|FALSE}}==
<syntaxhighlight lang="false">["Move disk from "$!\" to "$!\"
"]p: { to from }
[n;0>[n;1-n: @\ h;! @\ p;! \@ h;! \@ n;1+n:]?]h: { via to from }
4n:["right"]["middle"]["left"]h;!%%%</syntaxhighlight>
=={{header|Fermat}}==
<syntaxhighlight lang="fermat">Func Hanoi( n, f, t, v ) =
if n = 0 then
!'';
else
Hanoi(n - 1, f, v, t);
!f;!' -> ';!t;!', ';
Hanoi(n - 1, v, t, f)
fi.</syntaxhighlight>
{{out}}<pre>1 -> 3, 1 -> 2, 3 -> 2, 1 -> 3, 2 -> 1, 2 -> 3, 1 -> 3, 1 -> 2, 3 -> 2, 3 -> 1, 2 -> 1, 3 -> 2, 1 -> 3, 1 -> 2, 3 -> 2,</pre>
=={{header|FOCAL}}==
<syntaxhighlight lang="focal">01.10 S N=4;S S=1;S V=2;S T=3
01.20 D 2
01.30 Q
02.02 S N(D)=N(D)-1;I (N(D)),2.2,2.04
02.04 S D=D+1
02.06 S N(D)=N(D-1);S S(D)=S(D-1)
02.08 S T(D)=V(D-1);S V(D)=T(D-1)
02.10 D 2
02.12 S D=D-1
02.14 D 3
02.16 S A=S(D);S S(D)=V(D);S V(D)=A
02.18 G 2.02
02.20 D 3
03.10 T %1,"MOVE DISK FROM POLE",S(D)
03.20 T " TO POLE",T(D),!</syntaxhighlight>
{{out}}
<pre>MOVE DISK FROM POLE= 1 TO POLE= 2
MOVE DISK FROM POLE= 1 TO POLE= 3
MOVE DISK FROM POLE= 2 TO POLE= 3
MOVE DISK FROM POLE= 1 TO POLE= 2
MOVE DISK FROM POLE= 3 TO POLE= 1
MOVE DISK FROM POLE= 3 TO POLE= 2
MOVE DISK FROM POLE= 1 TO POLE= 2
MOVE DISK FROM POLE= 1 TO POLE= 3
MOVE DISK FROM POLE= 2 TO POLE= 3
MOVE DISK FROM POLE= 2 TO POLE= 1
MOVE DISK FROM POLE= 3 TO POLE= 1
MOVE DISK FROM POLE= 2 TO POLE= 3
MOVE DISK FROM POLE= 1 TO POLE= 2
MOVE DISK FROM POLE= 1 TO POLE= 3
MOVE DISK FROM POLE= 2 TO POLE= 3</pre>
=={{header|Forth}}==
With locals:
<syntaxhighlight lang="forth">CREATE peg1 ," left "
CREATE peg2 ," middle "
CREATE peg3 ," right "
: .$ COUNT TYPE ;
: MOVE-DISK
LOCALS| via to from n |
n 1 =
IF CR ." Move disk from " from .$ ." to " to .$
ELSE n 1- from via to RECURSE
1 from to via RECURSE
n 1- via to from RECURSE
THEN ;</syntaxhighlight>
Without locals, executable pegs:
<syntaxhighlight lang="forth">: left ." left" ;
: right ." right" ;
: middle ." middle" ;
: move-disk ( v t f n -- v t f )
dup 0= if drop exit then
1- >R
rot swap R@ ( t v f n-1 ) recurse
rot swap
2dup cr ." Move disk from " execute ." to " execute
swap rot R> ( f t v n-1 ) recurse
swap rot ;
: hanoi ( n -- )
1 max >R ['] right ['] middle ['] left R> move-disk drop drop drop ;</syntaxhighlight>
=={{header|Fortran}}==
{{works with|Fortran|90 and later}}
<syntaxhighlight lang="fortran">PROGRAM TOWER
CALL Move(4, 1, 2, 3)
CONTAINS
RECURSIVE SUBROUTINE Move(ndisks, from, to, via)
INTEGER, INTENT (IN) :: ndisks, from, to, via
IF (ndisks == 1) THEN
WRITE(*, "(A,I1,A,I1)") "Move disk from pole ", from, " to pole ", to
ELSE
CALL Move(ndisks-1, from, via, to)
CALL Move(1, from, to, via)
CALL Move(ndisks-1, via, to, from)
END IF
END SUBROUTINE Move
END PROGRAM TOWER</syntaxhighlight>
{{ More informative version }}
<syntaxhighlight lang="fortran">
PROGRAM TOWER2
CALL Move(4, 1, 2, 3)
CONTAINS
RECURSIVE SUBROUTINE Move(ndisks, from, via, to)
INTEGER, INTENT (IN) :: ndisks, from, via, to
IF (ndisks > 1) THEN
CALL Move(ndisks-1, from, to, via)
WRITE(*, "(A,I1,A,I1,A,I1)") "Move disk ", ndisks, " from pole ", from, " to pole ", to
Call Move(ndisks-1,via,from,to)
ELSE
WRITE(*, "(A,I1,A,I1,A,I1)") "Move disk ", ndisks, " from pole ", from, " to pole ", to
END IF
END SUBROUTINE Move
END PROGRAM TOWER2 </syntaxhighlight>
=={{header|FreeBASIC}}==
<syntaxhighlight lang="freebasic">' FB 1.05.0 Win64
Sub move(n As Integer, from As Integer, to_ As Integer, via As Integer)
If n > 0 Then
move(n - 1, from, via, to_)
Print "Move disk"; n; " from pole"; from; " to pole"; to_
move(n - 1, via, to_, from)
End If
End Sub
Print "Three disks" : Print
move 3, 1, 2, 3
Print
Print "Four disks" : Print
move 4, 1, 2, 3
Print "Press any key to quit"
Sleep</syntaxhighlight>
{{out}}
<pre>
Three disks
Move disk 1 from pole 1 to pole 2
Move disk 2 from pole 1 to pole 3
Move disk 1 from pole 2 to pole 3
Move disk 3 from pole 1 to pole 2
Move disk 1 from pole 3 to pole 1
Move disk 2 from pole 3 to pole 2
Move disk 1 from pole 1 to pole 2
Four disks
Move disk 1 from pole 1 to pole 3
Move disk 2 from pole 1 to pole 2
Move disk 1 from pole 3 to pole 2
Move disk 3 from pole 1 to pole 3
Move disk 1 from pole 2 to pole 1
Move disk 2 from pole 2 to pole 3
Move disk 1 from pole 1 to pole 3
Move disk 4 from pole 1 to pole 2
Move disk 1 from pole 3 to pole 2
Move disk 2 from pole 3 to pole 1
Move disk 1 from pole 2 to pole 1
Move disk 3 from pole 3 to pole 2
Move disk 1 from pole 1 to pole 3
Move disk 2 from pole 1 to pole 2
Move disk 1 from pole 3 to pole 2
</pre>
=={{header|Frink}}==
<syntaxhighlight lang="frink">
/** Set up the recursive call for n disks */
hanoi[n] := hanoi[n, 1, 3, 2]
/** The recursive call. */
hanoi[n, source, target, aux] :=
{
if n > 0
{
hanoi[n-1, source, aux, target]
println["Move from $source to $target"]
hanoi[n-1, aux, target, source]
}
}
hanoi[7]
</syntaxhighlight>
=={{header|FutureBasic}}==
<syntaxhighlight lang="futurebasic">window 1, @"Towers of Hanoi", ( 0, 0, 300, 300 )
void local fn Move( n as long, fromPeg as long, toPeg as long, viaPeg as long )
if n > 0
fn Move( n-1, fromPeg, viaPeg, toPeg )
print "Move disk from "; fromPeg; " to "; toPeg
fn Move( n-1, viaPeg, toPeg, fromPeg )
end if
end fn
fn Move( 4, 1, 2, 3 )
print
print "Towers of Hanoi puzzle solved."
HandleEvents</syntaxhighlight>
Output:
<pre>
Move disk from 1 to 3
Move disk from 1 to 2
Move disk from 3 to 2
Move disk from 1 to 3
Move disk from 2 to 1
Move disk from 2 to 3
Move disk from 1 to 3
Move disk from 1 to 2
Move disk from 3 to 2
Move disk from 3 to 1
Move disk from 2 to 1
Move disk from 3 to 2
Move disk from 1 to 3
Move disk from 1 to 2
Move disk from 3 to 2
Towers of Hanoi puzzle solved.
</pre>
=={{header|Fōrmulæ}}==
{{FormulaeEntry|page=https://formulae.org/?script=examples/Tower_of_Hanoi}}
'''Solution'''
[[File:Fōrmulæ - Tower of Hanoi 01.png]]
'''Test case'''
[[File:Fōrmulæ - Tower of Hanoi 02.png]]
[[File:Fōrmulæ - Tower of Hanoi 03.png]]
=={{header|Gambas}}==
{{trans|FreeBASIC}}
<syntaxhighlight lang="vbnet">Public Sub Main()
Print "Three disks\n"
move_(3, 1, 2, 3)
Print
Print "Four disks\n"
move_(4, 1, 2, 3)
End
Public Sub move_(n As Integer, from As Integer, to As Integer, via As Integer)
If n > 0 Then
move_(n - 1, from, via, to)
Print "Move disk "; n; " from pole "; from; " to pole "; to
move_(n - 1, via, to, from)
End If
End Sub </syntaxhighlight>
{{out}}
<pre>Same as FreeBASIC entry.</pre>
=={{header|GAP}}==
<syntaxhighlight lang="gap">Hanoi := function(n)
local move;
move := function(n, a, b, c) # from, through, to
if n = 1 then
Print(a, " -> ", c, "\n");
else
move(n - 1, a, c, b);
move(1, a, b, c);
move(n - 1, b, a, c);
fi;
end;
move(n, "A", "B", "C");
end;
Hanoi(1);
# A -> C
Hanoi(2);
# A -> B
# A -> C
# B -> C
Hanoi(3);
# A -> C
# A -> B
# C -> B
# A -> C
# B -> A
# B -> C
# A -> C</syntaxhighlight>
=={{header|Go}}==
<syntaxhighlight lang="go">package main
import "fmt"
// a towers of hanoi solver just has one method, play
type solver interface {
play(int)
}
func main() {
var t solver // declare variable of solver type
t = new(towers) // type towers must satisfy solver interface
t.play(4)
}
// towers is example of type satisfying solver interface
type towers struct {
// an empty struct. some other solver might fill this with some
// data representation, maybe for algorithm validation, or maybe for
// visualization.
}
// play is sole method required to implement solver type
func (t *towers) play(n int) {
// drive recursive solution, per task description
t.moveN(n, 1, 2, 3)
}
// recursive algorithm
func (t *towers) moveN(n, from, to, via int) {
if n > 0 {
t.moveN(n-1, from, via, to)
t.move1(from, to)
t.moveN(n-1, via, to, from)
}
}
// example function prints actions to screen.
// enhance with validation or visualization as needed.
func (t *towers) move1(from, to int) {
fmt.Println("move disk from rod", from, "to rod", to)
}</syntaxhighlight>
In other words:
<syntaxhighlight lang="go">package main
import "fmt"
func main() {
move(3, "A", "B", "C")
}
func move(n uint64, a, b, c string) {
if n > 0 {
move(n-1, a, c, b)
fmt.Println("Move disk from " + a + " to " + c)
move(n-1, b, a, c)
}
}</syntaxhighlight>
=={{header|Groovy}}==
Unlike most solutions here this solution manipulates more-or-less actual stacks of more-or-less actual rings.
<syntaxhighlight lang="groovy">def tail = { list, n -> def m = list.size(); list.subList([m - n, 0].max(),m) }
final STACK = [A:[],B:[],C:[]].asImmutable()
def report = { it -> }
def check = { it -> }
def moveRing = { from, to -> to << from.pop(); report(); check(to) }
def moveStack
moveStack = { from, to, using = STACK.values().find { !(it.is(from) || it.is(to)) } ->
if (!from) return
def n = from.size()
moveStack(tail(from, n-1), using, to)
moveRing(from, to)
moveStack(tail(using, n-1), to, from)
}</syntaxhighlight>
Test program:
<syntaxhighlight lang="groovy">enum Ring {
S('°'), M('o'), L('O'), XL('( )');
private sym
private Ring(sym) { this.sym=sym }
String toString() { sym }
}
report = { STACK.each { k, v -> println "${k}: ${v}" }; println() }
check = { to -> assert to == ([] + to).sort().reverse() }
Ring.values().reverseEach { STACK.A << it }
report()
check(STACK.A)
moveStack(STACK.A, STACK.C)</syntaxhighlight>
{{out}}
<pre style="height:30ex;overflow:scroll;">A: [( ), O, o, °]
B: []
C: []
A: [( ), O, o]
B: [°]
C: []
A: [( ), O]
B: [°]
C: [o]
A: [( ), O]
B: []
C: [o, °]
A: [( )]
B: [O]
C: [o, °]
A: [( ), °]
B: [O]
C: [o]
A: [( ), °]
B: [O, o]
C: []
A: [( )]
B: [O, o, °]
C: []
A: []
B: [O, o, °]
C: [( )]
A: []
B: [O, o]
C: [( ), °]
A: [o]
B: [O]
C: [( ), °]
A: [o, °]
B: [O]
C: [( )]
A: [o, °]
B: []
C: [( ), O]
A: [o]
B: [°]
C: [( ), O]
A: []
B: [°]
C: [( ), O, o]
A: []
B: []
C: [( ), O, o, °]</pre>
=={{header|Haskell}}==
Most of the programs on this page use an imperative approach
(i.e., print out movements as side effects during program execution).
Haskell favors a purely functional approach, where you would for example return a (lazy) list of movements from a to b via c:
<syntaxhighlight lang="haskell">hanoi :: Integer -> a -> a -> a -> [(a, a)]
hanoi 0 _ _ _ = []
hanoi n a b c = hanoi (n-1) a c b ++ [(a,b)] ++ hanoi (n-1) c b a</syntaxhighlight>
You can also do the above with one tail-recursion call:
<syntaxhighlight lang="haskell">hanoi :: Integer -> a -> a -> a -> [(a, a)]
hanoi n a b c = hanoiToList n a b c []
where
hanoiToList 0 _ _ _ l = l
hanoiToList n a b c l = hanoiToList (n-1) a c b ((a, b) : hanoiToList (n-1) c b a l)</syntaxhighlight>
One can use this function to produce output, just like the other programs:
<syntaxhighlight lang="haskell">hanoiIO n = mapM_ f $ hanoi n 1 2 3 where
f (x,y) = putStrLn $ "Move " ++ show x ++ " to " ++ show y</syntaxhighlight>
or, instead, one can of course also program imperatively, using the IO monad directly:
<syntaxhighlight lang="haskell">hanoiM :: Integer -> IO ()
hanoiM n = hanoiM' n 1 2 3 where
hanoiM' 0 _ _ _ = return ()
hanoiM' n a b c = do
hanoiM' (n-1) a c b
putStrLn $ "Move " ++ show a ++ " to " ++ show b
hanoiM' (n-1) c b a</syntaxhighlight>
or, defining it as a monoid, and adding some output:
<syntaxhighlight lang="haskell">-------------------------- HANOI -------------------------
hanoi ::
Int ->
String ->
String ->
String ->
[(String, String)]
hanoi 0 _ _ _ = mempty
hanoi n l r m =
hanoi (n - 1) l m r
<> [(l, r)]
<> hanoi (n - 1) m r l
--------------------------- TEST -------------------------
main :: IO ()
main = putStrLn $ showHanoi 5
------------------------- DISPLAY ------------------------
showHanoi :: Int -> String
showHanoi n =
unlines $
fmap
( \(from, to) ->
concat [justifyRight 5 ' ' from, " -> ", to]
)
(hanoi n "left" "right" "mid")
justifyRight :: Int -> Char -> String -> String
justifyRight n c = (drop . length) <*> (replicate n c <>)</syntaxhighlight>
{{Out}}
<pre> left -> right
left -> mid
right -> mid
left -> right
mid -> left
mid -> right
left -> right
left -> mid
right -> mid
right -> left
mid -> left
right -> mid
left -> right
left -> mid
right -> mid
left -> right
mid -> left
mid -> right
left -> right
mid -> left
right -> mid
right -> left
mid -> left
mid -> right
left -> right
left -> mid
right -> mid
left -> right
mid -> left
mid -> right
left -> right</pre>
=={{header|HolyC}}==
{{trans|C}}
<syntaxhighlight lang="holyc">U0 Move(U8 n, U8 from, U8 to, U8 via) {
if (n > 0) {
Move(n - 1, from, via, to);
Print("Move disk from pole %d to pole %d\n", from, to);
Move(n - 1, via, to, from);
}
}
Move(4, 1, 2, 3);</syntaxhighlight>
=={{header|Icon}} and {{header|Unicon}}==
The following is based on a solution in the Unicon book.
<syntaxhighlight lang="icon">procedure main(arglist)
hanoi(arglist[1]) | stop("Usage: hanoi n\n\rWhere n is the number of disks to move.")
end
#procedure hanoi(n:integer, needle1:1, needle2:2) # unicon shorthand for icon code 1,2,3 below
procedure hanoi(n, needle1, needle2) #: solve towers of hanoi by moving n disks from needle 1 to needle2 via other
local other
n := integer(0 < n) | runerr(n,101) # 1 ensure integer (this also ensures it's positive too)
/needle1 := 1 # 2 default
/needle2 := 2 # 3 default
if n = 1 then
write("Move disk from ", needle1, " to ", needle2)
else {
other := 6 - needle1 - needle2 # clever but somewhat un-iconish way to find other
hanoi(n-1, needle1, other)
write("Move disk from ", needle1, " to ", needle2)
hanoi(n-1, other, needle2)
}
return
end</syntaxhighlight>
=={{header|Imp77}}==
<syntaxhighlight lang="Imp77">
%begin
%routine do hanoi(%integer n, f, t, u)
do hanoi(n - 1, f, u, t) %if n >= 2
print string("Move disk from ".itos(f,0)." to ".itos(t,0).to string(nl))
do hanoi(n - 1, u, t, f) %if n >= 2
%end
do hanoi(4, 1, 2, 3)
print string("Towers of Hanoi puzzle completed!".to string(nl))
%end %of %program
</syntaxhighlight>
{{out}}
<pre>
Move disk from 1 to 3
Move disk from 1 to 2
Move disk from 3 to 2
Move disk from 1 to 3
Move disk from 2 to 1
Move disk from 2 to 3
Move disk from 1 to 3
Move disk from 1 to 2
Move disk from 3 to 2
Move disk from 3 to 1
Move disk from 2 to 1
Move disk from 3 to 2
Move disk from 1 to 3
Move disk from 1 to 2
Move disk from 3 to 2
Towers of Hanoi puzzle completed!
</pre>
=={{header|Inform 7}}==
<syntaxhighlight lang="inform7">Hanoi is a room.
A post is a kind of supporter. A post is always fixed in place.
The left post, the middle post, and the right post are posts in Hanoi.
A disk is a kind of supporter.
The red disk is a disk on the left post.
The orange disk is a disk on the red disk.
The yellow disk is a disk on the orange disk.
The green disk is a disk on the yellow disk.
Definition: a disk is topmost if nothing is on it.
When play begins:
move 4 disks from the left post to the right post via the middle post.
To move (N - number) disk/disks from (FP - post) to (TP - post) via (VP - post):
if N > 0:
move N - 1 disks from FP to VP via TP;
say "Moving a disk from [FP] to [TP]...";
let D be a random topmost disk enclosed by FP;
if a topmost disk (called TD) is enclosed by TP, now D is on TD;
otherwise now D is on TP;
move N - 1 disks from VP to TP via FP.</syntaxhighlight>
=={{header|Io}}==
<syntaxhighlight lang="io">hanoi := method(n, from, to, via,
if (n == 1) then (
writeln("Move from ", from, " to ", to)
) else (
hanoi(n - 1, from, via, to )
hanoi(1 , from, to , via )
hanoi(n - 1, via , to , from)
)
)</syntaxhighlight>
=={{header|Ioke}}==
<syntaxhighlight lang="ioke"> = method(n, f, u, t,
if(n < 2,
"#{f} --> #{t}" println,
H(n - 1, f, t, u)
"#{f} --> #{t}" println
H(n - 1, u, f, t)
)
)
hanoi = method(n,
H(n, 1, 2, 3)
)</syntaxhighlight>
=={{header|J}}==
'''Solutions'''
<syntaxhighlight lang="j">H =: i.@,&2 ` (({&0 2 1,0 2,{&1 0 2)@$:@<:) @. * NB. tacit using anonymous recursion</syntaxhighlight>
{{out|Example use}}
<syntaxhighlight lang="j"> H 3
0 2
0 1
2 1
0 2
1 2
1 0
2 0</syntaxhighlight>
The result is a 2-column table; a row <tt>i,j</tt> is interpreted as: move a disk (the top disk) from peg <tt>i</tt> to peg<tt> j</tt> .
Or, using explicit rather than implicit code:
<syntaxhighlight lang="j">H1=: monad define NB. explicit equivalent of H
if. y do.
({&0 2 1 , 0 2 , {&1 0 2) H1 y-1
else.
i.0 2
end.
)</syntaxhighlight>
The usage here is the same:
<pre> H1 2
0 1
0 2
1 2</pre>
;Alternative solution
If a textual display is desired, similar to some of the other solutions here (counting from 1 instead of 0, tracking which disk is on the top of the stack, and of course formatting the result for a human reader instead of providing a numeric result):
<syntaxhighlight lang="j">hanoi=: monad define
moves=. H y
disks=. $~` ((],[,]) $:@<:) @.* y
('move disk ';' from peg ';' to peg ');@,."1 ":&.>disks,.1+moves
)</syntaxhighlight>
{{out|Demonstration}}
<syntaxhighlight lang="j"> hanoi 3
move disk 1 from peg 1 to peg 3
move disk 2 from peg 1 to peg 2
move disk 1 from peg 3 to peg 2
move disk 3 from peg 1 to peg 3
move disk 1 from peg 2 to peg 1
move disk 2 from peg 2 to peg 3
move disk 1 from peg 1 to peg 3</syntaxhighlight>
=={{header|Java}}==
<syntaxhighlight lang="java">public void move(int n, int from, int to, int via) {
if (n == 1) {
System.out.println("Move disk from pole " + from + " to pole " + to);
} else {
move(n - 1, from, via, to);
move(1, from, to, via);
move(n - 1, via, to, from);
}
}</syntaxhighlight>
Where n is the number of disks to move and from, to, and via are the poles.
{{out|Example use}}
<syntaxhighlight lang="java">move(3, 1, 2, 3);</syntaxhighlight>
{{Out}}
<syntaxhighlight lang="java">Move disk from pole 1 to pole 2
Move disk from pole 1 to pole 3
Move disk from pole 2 to pole 3
Move disk from pole 1 to pole 2
Move disk from pole 3 to pole 1
Move disk from pole 3 to pole 2
Move disk from pole 1 to pole 2</syntaxhighlight>
=={{header|JavaScript}}==
===ES5===
<syntaxhighlight lang="javascript">function move(n, a, b, c) {
if (n > 0) {
move(n-1, a, c, b);
console.log("Move disk from " + a + " to " + c);
move(n-1, b, a, c);
}
}
move(4, "A", "B", "C");</syntaxhighlight>
Or, as a functional expression, rather than a statement with side effects:
<syntaxhighlight lang="javascript">(function () {
// hanoi :: Int -> String -> String -> String -> [[String, String]]
function hanoi(n, a, b, c) {
return n ? hanoi(n - 1, a, c, b)
.concat([
[a, b]
])
.concat(hanoi(n - 1, c, b, a)) : [];
}
return hanoi(3, 'left', 'right', 'mid')
.map(function (d) {
return d[0] + ' -> ' + d[1];
});
})();</syntaxhighlight>
{{Out}}
<syntaxhighlight lang="javascript">["left -> right", "left -> mid",
"right -> mid", "left -> right",
"mid -> left", "mid -> right",
"left -> right"]</syntaxhighlight>
===ES6===
<syntaxhighlight lang="javascript">(() => {
"use strict";
// ----------------- TOWERS OF HANOI -----------------
// hanoi :: Int -> String -> String ->
// String -> [[String, String]]
const hanoi = n =>
(a, b, c) => {
const go = hanoi(n - 1);
return n
? [
...go(a, c, b),
[a, b],
...go(c, b, a)
]
: [];
};
// ---------------------- TEST -----------------------
return hanoi(3)("left", "right", "mid")
.map(d => `${d[0]} -> ${d[1]}`)
.join("\n");
})();</syntaxhighlight>
{{Out}}
<pre>left -> right
left -> mid
right -> mid
left -> right
mid -> left
mid -> right
left -> right</pre>
=={{header|Joy}}==
<syntaxhighlight lang="joy">DEFINE hanoi == [[rolldown] infra] dip
[[[null] [pop pop] ]
[[dup2 [[rotate] infra] dip pred]
[[dup rest put] dip
[[swap] infra] dip pred]
[]]]
condnestrec.</syntaxhighlight>
Using it (5 is the number of disks.)
<syntaxhighlight lang="joy">[source destination temp] 5 hanoi.</syntaxhighlight>
=={{header|jq}}==
{{works with|jq|1.4}}
The algorithm used here is used elsewhere on this page but it is worthwhile pointing out that it can also be read as a proof that:
(a) move(n;"A";"B";"C") will logically succeed for n>=0; and
(b) move(n;"A";"B";"C") will generate the sequence of moves, assuming sufficient computing resources.
The proof of (a) is by induction:
* As explained in the comments, the algorithm establishes that move(n;x;y;z) is possible for all n>=0 and distinct x,y,z if move(n-1;x;y;z)) is possible;
* Since move(0;x;y;z) evidently succeeds, (a) is established by induction.
The truth of (b) follows from the fact that the algorithm emits an instruction of what to do when moving a single disk.
<syntaxhighlight lang="jq"># n is the number of disks to move from From to To
def move(n; From; To; Via):
if n > 0 then
# move all but the largest at From to Via (according to the rules):
move(n-1; From; Via; To),
# ... so the largest disk at From is now free to move to its final destination:
"Move disk from \(From) to \(To)",
# Move the remaining disks at Via to To:
move(n-1; Via; To; From)
else empty
end;</syntaxhighlight>
'''Example''':
move(5; "A"; "B"; "C")
=={{header|Jsish}}==
From Javascript ES5 entry.
<syntaxhighlight lang="javascript">/* Towers of Hanoi, in Jsish */
function move(n, a, b, c) {
if (n > 0) {
move(n-1, a, c, b);
puts("Move disk from " + a + " to " + c);
move(n-1, b, a, c);
}
}
if (Interp.conf('unitTest')) move(4, "A", "B", "C");
/*
=!EXPECTSTART!=
Move disk from A to B
Move disk from A to C
Move disk from B to C
Move disk from A to B
Move disk from C to A
Move disk from C to B
Move disk from A to B
Move disk from A to C
Move disk from B to C
Move disk from B to A
Move disk from C to A
Move disk from B to C
Move disk from A to B
Move disk from A to C
Move disk from B to C
=!EXPECTEND!=
*/</syntaxhighlight>
{{out}}
<pre>prompt$ jsish -u towersOfHanoi.jsi
[PASS] towersOfHanoi.jsi</pre>
=={{header|Julia}}==
{{trans|R}}
<syntaxhighlight lang="julia">
function solve(n::Integer, from::Integer, to::Integer, via::Integer)
if n == 1
println("Move disk from $from to $to")
else
solve(n - 1, from, via, to)
solve(1, from, to, via)
solve(n - 1, via, to, from)
end
end
solve(4, 1, 2, 3)
</syntaxhighlight>
{{out}}
<pre>
Move disk from 1 to 3
Move disk from 1 to 2
Move disk from 3 to 2
Move disk from 1 to 3
Move disk from 2 to 1
Move disk from 2 to 3
Move disk from 1 to 3
Move disk from 1 to 2
Move disk from 3 to 2
Move disk from 3 to 1
Move disk from 2 to 1
Move disk from 3 to 2
Move disk from 1 to 3
Move disk from 1 to 2
Move disk from 3 to 2
</pre>
=={{header|K}}==
<syntaxhighlight lang="k"> h:{[n;a;b;c]if[n>0;_f[n-1;a;c;b];`0:,//$($n,":",$a,"->",$b,"\n");_f[n-1;c;b;a]]}
h[4;1;2;3]
1:1->3
2:1->2
1:3->2
3:1->3
1:2->1
2:2->3
1:1->3
4:1->2
1:3->2
2:3->1
1:2->1
3:3->2
1:1->3
2:1->2
1:3->2</syntaxhighlight>
The disk to move in the i'th step is the same as the position of the leftmost 1 in the binary representation of 1..2^n.
<syntaxhighlight lang="k"> s:();{[n;a;b;c]if[n>0;_f[n-1;a;c;b];s,:n;_f[n-1;c;b;a]]}[4;1;2;3];s
1 2 1 3 1 2 1 4 1 2 1 3 1 2 1
1_{*1+&|x}'a:(2_vs!_2^4)
1 2 1 3 1 2 1 4 1 2 1 3 1 2 1</syntaxhighlight>
=={{header|Klingphix}}==
{{trans|MiniScript}}
<syntaxhighlight lang="klingphix">include ..\Utilitys.tlhy
:moveDisc %B !B %C !C %A !A %n !n { n A C B }
$n [
$n 1 - $A $B $C moveDisc
( "Move disc " $n " from pole " $A " to pole " $C ) lprint nl
$n 1 - $B $C $A moveDisc
] if
;
{ Move disc 3 from pole 1 to pole 3, with pole 2 as spare }
3 1 3 2 moveDisc
" " input</syntaxhighlight>
{{out}}
<pre>Move disc 1 from pole 1 to pole 3
Move disc 2 from pole 1 to pole 2
Move disc 1 from pole 3 to pole 2
Move disc 3 from pole 1 to pole 3
Move disc 1 from pole 2 to pole 1
Move disc 2 from pole 2 to pole 3
Move disc 1 from pole 1 to pole 3</pre>
=={{header|Kotlin}}==
<syntaxhighlight lang="scala">// version 1.1.0
class Hanoi(disks: Int) {
private var moves = 0
init {
println("Towers of Hanoi with $disks disks:\n")
move(disks, 'L', 'C', 'R')
println("\nCompleted in $moves moves\n")
}
private fun move(n: Int, from: Char, to: Char, via: Char) {
if (n > 0) {
move(n - 1, from, via, to)
moves++
println("Move disk $n from $from to $to")
move(n - 1, via, to, from)
}
}
}
fun main(args: Array<String>) {
Hanoi(3)
Hanoi(4)
}</syntaxhighlight>
{{out}}
<pre>
Towers of Hanoi with 3 disks:
Move disk 1 from L to C
Move disk 2 from L to R
Move disk 1 from C to R
Move disk 3 from L to C
Move disk 1 from R to L
Move disk 2 from R to C
Move disk 1 from L to C
Completed in 7 moves
Towers of Hanoi with 4 disks:
Move disk 1 from L to R
Move disk 2 from L to C
Move disk 1 from R to C
Move disk 3 from L to R
Move disk 1 from C to L
Move disk 2 from C to R
Move disk 1 from L to R
Move disk 4 from L to C
Move disk 1 from R to C
Move disk 2 from R to L
Move disk 1 from C to L
Move disk 3 from R to C
Move disk 1 from L to R
Move disk 2 from L to C
Move disk 1 from R to C
Completed in 15 moves
</pre>
=={{header|Lambdatalk}}==
<syntaxhighlight lang="scheme">
PSEUDO-CODE:
hanoi disks from A to B via C
if no disks
then stop
else hanoi upper disks from A to C via B
move lower disk from A to B
hanoi upper disks from C to B via A
CODE:
{def hanoi
{lambda {:disks :a :b :c}
{if {A.empty? :disks}
then
else {hanoi {A.rest :disks} :a :c :b}
{div > move {A.first :disks} from :a to :b}
{hanoi {A.rest :disks} :c :b :a} }}}
-> hanoi
{hanoi {A.new ==== === == =} A B C}
->
> move = from A to C
> move == from A to B
> move = from C to B
> move === from A to C
> move = from B to A
> move == from B to C
> move = from A to C
> move ==== from A to B
> move = from C to B
> move == from C to A
> move = from B to A
> move === from C to B
> move = from A to C
> move == from A to B
> move = from C to B
</syntaxhighlight>
=={{header|Lasso}}==
<syntaxhighlight lang="lasso">#!/usr/bin/lasso9
define towermove(
disks::integer,
a,b,c
) => {
if(#disks > 0) => {
towermove(#disks - 1, #a, #c, #b )
stdoutnl("Move disk from " + #a + " to " + #c)
towermove(#disks - 1, #b, #a, #c )
}
}
towermove((integer($argv -> second || 3)), "A", "B", "C")</syntaxhighlight>
Called from command line:
<syntaxhighlight lang="lasso">./towers</syntaxhighlight>
{{out}}
<pre>Move disk from A to C
Move disk from A to B
Move disk from C to B
Move disk from A to C
Move disk from B to A
Move disk from B to C
Move disk from A to C</pre>
Called from command line:
<syntaxhighlight lang="lasso">./towers 4</syntaxhighlight>
{{out}}
<pre>Move disk from A to B
Move disk from A to C
Move disk from B to C
Move disk from A to B
Move disk from C to A
Move disk from C to B
Move disk from A to B
Move disk from A to C
Move disk from B to C
Move disk from B to A
Move disk from C to A
Move disk from B to C
Move disk from A to B
Move disk from A to C
Move disk from B to C</pre>
=={{header|Liberty BASIC}}==
This looks much better with a GUI interface.
<syntaxhighlight lang="lb"> source$ ="A"
via$ ="B"
target$ ="C"
call hanoi 4, source$, target$, via$ ' ie call procedure to move legally 4 disks from peg A to peg C via peg B
wait
sub hanoi numDisks, source$, target$, via$
if numDisks =0 then
exit sub
else
call hanoi numDisks -1, source$, via$, target$
print " Move disk "; numDisks; " from peg "; source$; " to peg "; target$
call hanoi numDisks -1, via$, target$, source$
end if
end sub
end</syntaxhighlight>
=={{header|Lingo}}==
<syntaxhighlight lang="lingo">on hanoi (n, a, b, c)
if n > 0 then
hanoi(n-1, a, c, b)
put "Move disk from" && a && "to" && c
hanoi(n-1, b, a, c)
end if
end</syntaxhighlight>
<syntaxhighlight lang="lingo">hanoi(3, "A", "B", "C")
-- "Move disk from A to C"
-- "Move disk from A to B"
-- "Move disk from C to B"
-- "Move disk from A to C"
-- "Move disk from B to A"
-- "Move disk from B to C"
-- "Move disk from A to C"</syntaxhighlight>
=={{header|Logo}}==
<syntaxhighlight lang="logo">to move :n :from :to :via
if :n = 0 [stop]
move :n-1 :from :via :to
(print [Move disk from] :from [to] :to)
move :n-1 :via :to :from
end
move 4 "left "middle "right</syntaxhighlight>
=={{header|Logtalk}}==
<syntaxhighlight lang="logtalk">:- object(hanoi).
:- public(run/1).
:- mode(run(+integer), one).
:- info(run/1, [
comment is 'Solves the towers of Hanoi problem for the specified number of disks.',
argnames is ['Disks']]).
run(Disks) :-
move(Disks, left, middle, right).
move(1, Left, _, Right):-
!,
report(Left, Right).
move(Disks, Left, Aux, Right):-
Disks2 is Disks - 1,
move(Disks2, Left, Right, Aux),
report(Left, Right),
move(Disks2, Aux, Left, Right).
report(Pole1, Pole2):-
write('Move a disk from '),
writeq(Pole1),
write(' to '),
writeq(Pole2),
write('.'),
nl.
:- end_object.</syntaxhighlight>
=={{header|LOLCODE}}==
<syntaxhighlight lang="lolcode">HAI 1.2
HOW IZ I HANOI YR N AN YR SRC AN YR DST AN YR VIA
BTW VISIBLE SMOOSH "HANOI N=" N " SRC=" SRC " DST=" DST " VIA=" VIA MKAY
BOTH SAEM N AN 0, O RLY?
YA RLY
BTW VISIBLE "Done."
GTFO
NO WAI
I HAS A LOWER ITZ DIFF OF N AN 1
I IZ HANOI YR LOWER AN YR SRC AN YR VIA AN YR DST MKAY
VISIBLE SMOOSH "Move disc " N " from " SRC " to " DST MKAY
I IZ HANOI YR LOWER AN YR VIA AN YR DST AN YR SRC MKAY
OIC
IF U SAY SO
I IZ HANOI YR 4 AN YR 1 AN YR 2 AN YR 3 MKAY
KTHXBYE
</syntaxhighlight>
=={{header|Lua}}==
<syntaxhighlight lang="lua">function move(n, src, dst, via)
if n > 0 then
move(n - 1, src, via, dst)
print(src, 'to', dst)
move(n - 1, via, dst, src)
end
end
move(4, 1, 2, 3)</syntaxhighlight>
{{More informative version }}
<syntaxhighlight lang="lua">
function move(n, src, via, dst)
if n > 0 then
move(n - 1, src, dst, via)
print('Disk ',n,' from ' ,src, 'to', dst)
move(n - 1, via, src, dst)
end
end
move(4, 1, 2, 3)
</syntaxhighlight>
===Hanoi Iterative===
<syntaxhighlight lang="lua">
#!/usr/bin/env luajit
local function printf(fmt, ...) io.write(string.format(fmt, ...)) end
local runs=0
local function move(tower, from, to)
if #tower[from]==0
or (#tower[to]>0
and tower[from][#tower[from]]>tower[to][#tower[to]]) then
to,from=from,to
end
if #tower[from]>0 then
tower[to][#tower[to]+1]=tower[from][#tower[from]]
tower[from][#tower[from]]=nil
io.write(tower[to][#tower[to]],":",from, "→", to, " ")
end
end
local function hanoi(n)
local src,dst,via={},{},{}
local tower={src,dst,via}
for i=1,n do src[i]=n-i+1 end
local one,nxt,lst
if n%2==1 then -- odd
one,nxt,lst=1,2,3
else
one,nxt,lst=1,3,2
end
--repeat
::loop::
move(tower, one, nxt)
if #dst==n then return end
move(tower, one, lst)
one,nxt,lst=nxt,lst,one
goto loop
--until false
end
local num=arg[1] and tonumber(arg[1]) or 4
hanoi(num)
</syntaxhighlight>
{{out}}
<pre>
> ./hanoi_iter.lua 5
1:1→2 2:1→3 1:2→3 3:1→2 1:3→1 2:3→2 1:1→2 4:1→3 1:2→3 2:2→1 1:3→1 3:2→3 1:1→2 2:1→3 1:2→3 5:1→2 1:3→1 2:3→2 1:1→2 3:3→1 1:2→3 2:2→1 1:3→1 4:3→2 1:1→2 2:1→3 1:2→3 3:1→2 1:3→1 2:3→2 1:1→2
</pre>
===Hanoi Bitwise Fast===
<syntaxhighlight lang="lua">
#!/usr/bin/env luajit
-- binary solution
local bit=require"bit"
local band,bor=bit.band,bit.bor
local function hanoi(n)
local even=(n-1)%2
for m=1,2^n-1 do
io.write(m,":",band(m,m-1)%3+1, "→", (bor(m,m-1)+1)%3+1, " ")
end
end
local num=arg[1] and tonumber(arg[1]) or 4
hanoi(num)
</syntaxhighlight>
{{out}}
<pre>
> ./hanoi_bit.lua 4
1:1→3 2:1→2 3:3→2 4:1→3 5:2→1 6:2→3 7:1→3 8:1→2 9:3→2 10:3→1 11:2→1 12:3→2 13:1→3 14:1→2 15:3→2
> time ./hanoi_bit.lua 30 >/dev/null ; on AMD FX-8350 @ 4 GHz
./hanoi_bit.lua 30 > /dev/null 297,40s user 1,39s system 99% cpu 4:59,01 total
</pre>
=={{header|M2000 Interpreter}}==
{{trans|FreeBasic}}
<syntaxhighlight lang="m2000 interpreter">
Module Hanoi {
Rem HANOI TOWERS
Print "Three disks" : Print
move(3, 1, 2, 3)
Print
Print "Four disks" : Print
move(4, 1, 2, 3)
Sub move(n, from, to, via)
If n <=0 Then Exit Sub
move(n - 1, from, via, to)
Print "Move disk"; n; " from pole"; from; " to pole"; to
move(n - 1, via, to, from)
End Sub
}
Hanoi
</syntaxhighlight>
{{out}}
same as in FreeBasic
=={{header|MACRO-11}}==
<syntaxhighlight lang="macro11"> .TITLE HANOI
.MCALL .PRINT,.EXIT
HANOI:: MOV #4,R2
MOV #61,R3
MOV #62,R4
MOV #63,R5
JSR PC,MOVE
.EXIT
MOVE: DEC R2
BLT 1$
MOV R2,-(SP)
MOV R3,-(SP)
MOV R4,-(SP)
MOV R5,-(SP)
MOV R5,R0
MOV R4,R5
MOV R0,R4
JSR PC,MOVE
MOV (SP)+,R5
MOV (SP)+,R4
MOV (SP)+,R3
MOV (SP)+,R2
MOVB R3,3$
MOVB R4,4$
.PRINT #2$
MOV R3,R0
MOV R4,R3
MOV R5,R4
MOV R0,R5
BR MOVE
1$: RTS PC
2$: .ASCII /MOVE DISK FROM PEG /
3$: .ASCII /* TO PEG /
4$: .ASCIZ /*/
.EVEN
.END HANOI</syntaxhighlight>
{{out}}
<pre>MOVE DISK FROM PEG 1 TO PEG 3
MOVE DISK FROM PEG 1 TO PEG 2
MOVE DISK FROM PEG 2 TO PEG 3
MOVE DISK FROM PEG 1 TO PEG 3
MOVE DISK FROM PEG 3 TO PEG 1
MOVE DISK FROM PEG 3 TO PEG 2
MOVE DISK FROM PEG 2 TO PEG 1
MOVE DISK FROM PEG 1 TO PEG 2
MOVE DISK FROM PEG 2 TO PEG 3
MOVE DISK FROM PEG 2 TO PEG 1
MOVE DISK FROM PEG 1 TO PEG 3
MOVE DISK FROM PEG 2 TO PEG 3
MOVE DISK FROM PEG 3 TO PEG 2
MOVE DISK FROM PEG 3 TO PEG 1
MOVE DISK FROM PEG 1 TO PEG 2</pre>
=={{header|MAD}}==
<syntaxhighlight lang="mad"> NORMAL MODE IS INTEGER
DIMENSION LIST(100)
SET LIST TO LIST
VECTOR VALUES MOVFMT =
0 $20HMOVE DISK FROM POLE ,I1,S1,8HTO POLE ,I1*$
INTERNAL FUNCTION(DUMMY)
ENTRY TO MOVE.
LOOP NUM = NUM - 1
WHENEVER NUM.E.0
PRINT FORMAT MOVFMT,FROM,DEST
OTHERWISE
SAVE RETURN
SAVE DATA NUM,FROM,VIA,DEST
TEMP=DEST
DEST=VIA
VIA=TEMP
MOVE.(0)
RESTORE DATA NUM,FROM,VIA,DEST
RESTORE RETURN
PRINT FORMAT MOVFMT,FROM,DEST
TEMP=FROM
FROM=VIA
VIA=TEMP
TRANSFER TO LOOP
END OF CONDITIONAL
FUNCTION RETURN
END OF FUNCTION
NUM = 4
FROM = 1
VIA = 2
DEST = 3
MOVE.(0)
END OF PROGRAM
</syntaxhighlight>
{{out}}
<pre>MOVE DISK FROM POLE 1 TO POLE 2
MOVE DISK FROM POLE 1 TO POLE 3
MOVE DISK FROM POLE 2 TO POLE 3
MOVE DISK FROM POLE 1 TO POLE 2
MOVE DISK FROM POLE 3 TO POLE 1
MOVE DISK FROM POLE 3 TO POLE 2
MOVE DISK FROM POLE 1 TO POLE 2
MOVE DISK FROM POLE 1 TO POLE 3
MOVE DISK FROM POLE 2 TO POLE 3
MOVE DISK FROM POLE 2 TO POLE 1
MOVE DISK FROM POLE 3 TO POLE 1
MOVE DISK FROM POLE 2 TO POLE 3
MOVE DISK FROM POLE 1 TO POLE 2
MOVE DISK FROM POLE 1 TO POLE 3
MOVE DISK FROM POLE 2 TO POLE 3</pre>
=={{header|Maple}}==
<syntaxhighlight lang="maple">
Hanoi := proc(n::posint,a,b,c)
if n = 1 then
printf("Move disk from tower %a to tower %a.\n",a,c);
else
Hanoi(n-1,a,c,b);
Hanoi(1,a,b,c);
Hanoi(n-1,b,a,c);
fi;
end:
printf("Moving 2 disks from tower A to tower C using tower B.\n");
Hanoi(2,A,B,C);
</syntaxhighlight>
{{out}}
Moving 2 disks from tower A to tower C using tower B.
Move disk from tower A to tower B.
Move disk from tower A to tower C.
Move disk from tower B to tower C.
=={{header|Mathematica}}/{{header|Wolfram Language}}==
<syntaxhighlight lang="mathematica">Hanoi[0, from_, to_, via_] := Null
Hanoi[n_Integer, from_, to_, via_] := (Hanoi[n-1, from, via, to];Print["Move disk from pole ", from, " to ", to, "."];Hanoi[n-1, via, to, from])</syntaxhighlight>
=={{header|MATLAB}}==
This is a direct translation from the Python example given in the Wikipedia entry for the Tower of Hanoi puzzle.
<syntaxhighlight lang="matlab">function towerOfHanoi(n,A,C,B)
if (n~=0)
towerOfHanoi(n-1,A,B,C);
disp(sprintf('Move plate %d from tower %d to tower %d',[n A C]));
towerOfHanoi(n-1,B,C,A);
end
end</syntaxhighlight>
{{out|Sample output}}
<pre>towerOfHanoi(3,1,3,2)
Move plate 1 from tower 1 to tower 3
Move plate 2 from tower 1 to tower 2
Move plate 1 from tower 3 to tower 2
Move plate 3 from tower 1 to tower 3
Move plate 1 from tower 2 to tower 1
Move plate 2 from tower 2 to tower 3
Move plate 1 from tower 1 to tower 3</pre>
=={{header|MiniScript}}==
<syntaxhighlight lang="miniscript">moveDisc = function(n, A, C, B)
if n == 0 then return
moveDisc n-1, A, B, C
print "Move disc " + n + " from pole " + A + " to pole " + C
moveDisc n-1, B, C, A
end function
// Move disc 3 from pole 1 to pole 3, with pole 2 as spare
moveDisc 3, 1, 3, 2</syntaxhighlight>
{{out}}
<pre>Move disc 1 from pole 1 to pole 3
Move disc 2 from pole 1 to pole 2
Move disc 1 from pole 3 to pole 2
Move disc 3 from pole 1 to pole 3
Move disc 1 from pole 2 to pole 1
Move disc 2 from pole 2 to pole 3
Move disc 1 from pole 1 to pole 3</pre>
=={{header|Miranda}}==
<syntaxhighlight lang="miranda">main :: [sys_message]
main = [Stdout (lay (map showmove (move 4 1 2 3)))]
showmove :: (num,num)->[char]
showmove (src,dest)
= "Move disk from pole " ++ show src ++ " to pole " ++ show dest
move :: num->*->*->*->[(*,*)]
move n src via dest
= [], if n=0
= left ++ [(src,dest)] ++ right, otherwise
where left = move (n-1) src dest via
right = move (n-1) via src dest</syntaxhighlight>
{{out}}
<pre>Move disk from pole 1 to pole 2
Move disk from pole 1 to pole 3
Move disk from pole 2 to pole 3
Move disk from pole 1 to pole 2
Move disk from pole 3 to pole 1
Move disk from pole 3 to pole 2
Move disk from pole 1 to pole 2
Move disk from pole 1 to pole 3
Move disk from pole 2 to pole 3
Move disk from pole 2 to pole 1
Move disk from pole 3 to pole 1
Move disk from pole 2 to pole 3
Move disk from pole 1 to pole 2
Move disk from pole 1 to pole 3
Move disk from pole 2 to pole 3</pre>
=={{header|MIPS Assembly}}==
<!--
Python equivalent:
def hanoi(n, From='A', To='B', Aux='C'):
def output():
print("Move disk %d from rod %s to rod %s" % (n, From, To))
if n==1:
output()
return
hanoi(n-1, From, Aux, To)
output()
hanoi(n-1, Aux, To, From)
hanoi(3)
--><syntaxhighlight lang="mips">
# Towers of Hanoi
# MIPS assembly implementation (tested with MARS)
# Source: https://stackoverflow.com/questions/50382420/hanoi-towers-recursive-solution-using-mips/50383530#50383530
.data
prompt: .asciiz "Enter a number: "
part1: .asciiz "\nMove disk "
part2: .asciiz " from rod "
part3: .asciiz " to rod "
.text
.globl main
main:
li $v0, 4 # print string
la $a0, prompt
syscall
li $v0, 5 # read integer
syscall
# parameters for the routine
add $a0, $v0, $zero # move to $a0
li $a1, 'A'
li $a2, 'B'
li $a3, 'C'
jal hanoi # call hanoi routine
li $v0, 10 # exit
syscall
hanoi:
#save in stack
addi $sp, $sp, -20
sw $ra, 0($sp)
sw $s0, 4($sp)
sw $s1, 8($sp)
sw $s2, 12($sp)
sw $s3, 16($sp)
add $s0, $a0, $zero
add $s1, $a1, $zero
add $s2, $a2, $zero
add $s3, $a3, $zero
addi $t1, $zero, 1
beq $s0, $t1, output
recur1:
addi $a0, $s0, -1
add $a1, $s1, $zero
add $a2, $s3, $zero
add $a3, $s2, $zero
jal hanoi
j output
recur2:
addi $a0, $s0, -1
add $a1, $s3, $zero
add $a2, $s2, $zero
add $a3, $s1, $zero
jal hanoi
exithanoi:
lw $ra, 0($sp) # restore registers from stack
lw $s0, 4($sp)
lw $s1, 8($sp)
lw $s2, 12($sp)
lw $s3, 16($sp)
addi $sp, $sp, 20 # restore stack pointer
jr $ra
output:
li $v0, 4 # print string
la $a0, part1
syscall
li $v0, 1 # print integer
add $a0, $s0, $zero
syscall
li $v0, 4 # print string
la $a0, part2
syscall
li $v0, 11 # print character
add $a0, $s1, $zero
syscall
li $v0, 4 # print string
la $a0, part3
syscall
li $v0, 11 # print character
add $a0, $s2, $zero
syscall
beq $s0, $t1, exithanoi
j recur2
</syntaxhighlight>
=={{header|МК-61/52}}==
<syntaxhighlight lang="text">^ 2 x^y П0 <-> 2 / {x} x#0 16
3 П3 2 П2 БП 20 3 П2 2 П3
1 П1 ПП 25 КППB ПП 28 КППA ПП 31
КППB ПП 34 КППA ИП1 ИП3 КППC ИП1 ИП2 КППC
ИП3 ИП2 КППC ИП1 ИП3 КППC ИП2 ИП1 КППC ИП2
ИП3 КППC ИП1 ИП3 КППC В/О ИП1 ИП2 БП 62
ИП2 ИП1 КППC ИП1 ИП2 ИП3 П1 -> П3 ->
П2 В/О 1 0 / + С/П КИП0 ИП0 x=0
89 3 3 1 ИНВ ^ ВП 2 С/П В/О</syntaxhighlight>
Instruction: РA = 56; РB = 60; РC = 72; N В/О С/П, where 2 <= N <= 7.
=={{header|Modula-2}}==
<syntaxhighlight lang="modula2">MODULE Towers;
FROM FormatString IMPORT FormatString;
FROM Terminal IMPORT WriteString,ReadChar;
PROCEDURE Move(n,from,to,via : INTEGER);
VAR buf : ARRAY[0..63] OF CHAR;
BEGIN
IF n>0 THEN
Move(n-1, from, via, to);
FormatString("Move disk %i from pole %i to pole %i\n", buf, n, from, to);
WriteString(buf);
Move(n-1, via, to, from)
END
END Move;
BEGIN
Move(3, 1, 3, 2);
ReadChar
END Towers.</syntaxhighlight>
=={{header|Modula-3}}==
<syntaxhighlight lang="modula3">MODULE Hanoi EXPORTS Main;
FROM IO IMPORT Put;
FROM Fmt IMPORT Int;
PROCEDURE doHanoi(n, from, to, using: INTEGER) =
BEGIN
IF n > 0 THEN
doHanoi(n - 1, from, using, to);
Put("move " & Int(from) & " --> " & Int(to) & "\n");
doHanoi(n - 1, using, to, from);
END;
END doHanoi;
BEGIN
doHanoi(4, 1, 2, 3);
END Hanoi.</syntaxhighlight>
=={{header|Monte}}==
<syntaxhighlight lang="monte">def move(n, fromPeg, toPeg, viaPeg):
if (n > 0):
move(n.previous(), fromPeg, viaPeg, toPeg)
traceln(`Move disk $n from $fromPeg to $toPeg`)
move(n.previous(), viaPeg, toPeg, fromPeg)
move(3, "left", "right", "middle")</syntaxhighlight>
=={{header|MoonScript}}==
<syntaxhighlight lang="moonscript">hanoi = (n, src, dest, via) ->
if n > 1
hanoi n-1, src, via, dest
print "#{src} -> #{dest}"
if n > 1
hanoi n-1, via, dest, src
hanoi 4,1,3,2</syntaxhighlight>
{{Out}}
<pre>1 -> 2
1 -> 3
2 -> 3
1 -> 2
3 -> 1
3 -> 2
1 -> 2
1 -> 3
2 -> 3
2 -> 1
3 -> 1
2 -> 3
1 -> 2
1 -> 3
2 -> 3</pre>
=={{header|Nemerle}}==
<syntaxhighlight lang="nemerle">using System;
using System.Console;
module Towers
{
Hanoi(n : int, from = 1, to = 3, via = 2) : void
{
when (n > 0)
{
Hanoi(n - 1, from, via, to);
WriteLine("Move disk from peg {0} to peg {1}", from, to);
Hanoi(n - 1, via, to, from);
}
}
Main() : void
{
Hanoi(4)
}
}</syntaxhighlight>
=={{header|NetRexx}}==
<syntaxhighlight lang="netrexx">/* NetRexx */
options replace format comments java crossref symbols binary
runSample(arg)
return
-- 09:02, 27 August 2022 (UTC)09:02, 27 August 2022 (UTC)09:02, 27 August 2022 (UTC)09:02, 27 August 2022 (UTC)09:02, 27 August 2022 (UTC)09:02, 27 August 2022 (UTC)09:02, 27 August 2022 (UTC)09:02, 27 August 2022 (UTC)09:02, 27 August 2022 (UTC)09:02, 27 August 2022 (UTC)09:02, 27 August 2022 (UTC)09:02, 27 August 2022 (UTC)09:02, 27 August 2022 (UTC)09:02, 27 August 2022 (UTC)09:02, 27 August 2022 (UTC)~~
method runSample(arg) private static
parse arg discs .
if discs = '', discs < 1 then discs = 4
say 'Minimum moves to solution:' 2 ** discs - 1
moves = move(discs)
say 'Solved in' moves 'moves.'
return
-- 09:02, 27 August 2022 (UTC)09:02, 27 August 2022 (UTC)09:02, 27 August 2022 (UTC)09:02, 27 August 2022 (UTC)09:02, 27 August 2022 (UTC)09:02, 27 August 2022 (UTC)09:02, 27 August 2022 (UTC)09:02, 27 August 2022 (UTC)09:02, 27 August 2022 (UTC)09:02, 27 August 2022 (UTC)09:02, 27 August 2022 (UTC)09:02, 27 August 2022 (UTC)09:02, 27 August 2022 (UTC)09:02, 27 August 2022 (UTC)09:02, 27 August 2022 (UTC)~~
method move(discs = int 4, towerFrom = int 1, towerTo = int 2, towerVia = int 3, moves = int 0) public static
if discs == 1 then do
moves = moves + 1
say 'Move disc from peg' towerFrom 'to peg' towerTo '- Move No:' Rexx(moves).right(5)
end
else do
moves = move(discs - 1, towerFrom, towerVia, towerTo, moves)
moves = move(1, towerFrom, towerTo, towerVia, moves)
moves = move(discs - 1, towerVia, towerTo, towerFrom, moves)
end
return moves
</syntaxhighlight>
{{out}}
<pre>
Minimum moves to solution: 15
Move disc from peg 1 to peg 3 - Move No: 1
Move disc from peg 1 to peg 2 - Move No: 2
Move disc from peg 3 to peg 2 - Move No: 3
Move disc from peg 1 to peg 3 - Move No: 4
Move disc from peg 2 to peg 1 - Move No: 5
Move disc from peg 2 to peg 3 - Move No: 6
Move disc from peg 1 to peg 3 - Move No: 7
Move disc from peg 1 to peg 2 - Move No: 8
Move disc from peg 3 to peg 2 - Move No: 9
Move disc from peg 3 to peg 1 - Move No: 10
Move disc from peg 2 to peg 1 - Move No: 11
Move disc from peg 3 to peg 2 - Move No: 12
Move disc from peg 1 to peg 3 - Move No: 13
Move disc from peg 1 to peg 2 - Move No: 14
Move disc from peg 3 to peg 2 - Move No: 15
Solved in 15 moves.
</pre>
=={{header|NewLISP}}==
<syntaxhighlight lang="lisp">(define (move n from to via)
(if (> n 0)
(move (- n 1) from via to
(print "move disk from pole " from " to pole " to "\n")
(move (- n 1) via to from))))
(move 4 1 2 3)</syntaxhighlight>
=={{header|Nim}}==
<syntaxhighlight lang="python">proc hanoi(disks: int; fromTower, toTower, viaTower: string) =
if disks != 0:
hanoi(disks - 1, fromTower, viaTower, toTower)
echo("Move disk ", disks, " from ", fromTower, " to ", toTower)
hanoi(disks - 1, viaTower, toTower, fromTower)
hanoi(4, "1", "2", "3")</syntaxhighlight>
{{out}}
<pre>Move disk 1 from 1 to 3
Move disk 2 from 1 to 2
Move disk 1 from 3 to 2
Move disk 3 from 1 to 3
Move disk 1 from 2 to 1
Move disk 2 from 2 to 3
Move disk 1 from 1 to 3
Move disk 4 from 1 to 2
Move disk 1 from 3 to 2
Move disk 2 from 3 to 1
Move disk 1 from 2 to 1
Move disk 3 from 3 to 2
Move disk 1 from 1 to 3
Move disk 2 from 1 to 2
Move disk 1 from 3 to 2</pre>
=={{header|Oberon-2}}==
{{trans|C}}
<syntaxhighlight lang="oberon2">MODULE Hanoi;
IMPORT Out;
PROCEDURE Move(n,from,via,to:INTEGER);
BEGIN
IF n > 1 THEN
Move(n-1,from,to,via);
Out.String("Move disk from pole ");
Out.Int(from,0);
Out.String(" to pole ");
Out.Int(to,0);
Out.Ln;
Move(n-1,via,from,to);
ELSE
Out.String("Move disk from pole ");
Out.Int(from,0);
Out.String(" to pole ");
Out.Int(to,0);
Out.Ln;
END;
END Move;
BEGIN
Move(4,1,2,3);
END Hanoi.
</syntaxhighlight>
{{out}}
<pre>Move disk from pole 1 to pole 2
Move disk from pole 1 to pole 3
Move disk from pole 2 to pole 3
Move disk from pole 1 to pole 2
Move disk from pole 3 to pole 1
Move disk from pole 3 to pole 2
Move disk from pole 1 to pole 2
Move disk from pole 1 to pole 3
Move disk from pole 2 to pole 3
Move disk from pole 2 to pole 1
Move disk from pole 3 to pole 1
Move disk from pole 2 to pole 3
Move disk from pole 1 to pole 2
Move disk from pole 1 to pole 3
Move disk from pole 2 to pole 3
</pre>
=={{header|Objeck}}==
<syntaxhighlight lang="objeck">class Hanoi {
function : Main(args : String[]) ~ Nil {
Move(4, 1, 2, 3);
}
function: Move(n:Int, f:Int, t:Int, v:Int) ~ Nil {
if(n = 1) {
"Move disk from pole {$f} to pole {$t}"->PrintLine();
}
else {
Move(n - 1, f, v, t);
Move(1, f, t, v);
Move(n - 1, v, t, f);
};
}
}</syntaxhighlight>
=={{header|Objective-C}}==
From [http://sites.google.com/site/vinodkshukla/code-snippets/objectivec-towersofhanoi here]
{{works with|GNUstep}}
It should be compatible with XCode/Cocoa on MacOS too.
The Interface - TowersOfHanoi.h:
<syntaxhighlight lang="objc">#import <Foundation/NSObject.h>
@interface TowersOfHanoi: NSObject {
int pegFrom;
int pegTo;
int pegVia;
int numDisks;
}
-(void) setPegFrom: (int) from andSetPegTo: (int) to andSetPegVia: (int) via andSetNumDisks: (int) disks;
-(void) movePegFrom: (int) from andMovePegTo: (int) to andMovePegVia: (int) via andWithNumDisks: (int) disks;
@end</syntaxhighlight>
The Implementation - TowersOfHanoi.m:
<syntaxhighlight lang="objc">#import "TowersOfHanoi.h"
@implementation TowersOfHanoi
-(void) setPegFrom: (int) from andSetPegTo: (int) to andSetPegVia: (int) via andSetNumDisks: (int) disks {
pegFrom = from;
pegTo = to;
pegVia = via;
numDisks = disks;
}
-(void) movePegFrom: (int) from andMovePegTo: (int) to andMovePegVia: (int) via andWithNumDisks: (int) disks {
if (disks == 1) {
printf("Move disk from pole %i to pole %i\n", from, to);
} else {
[self movePegFrom: from andMovePegTo: via andMovePegVia: to andWithNumDisks: disks-1];
[self movePegFrom: from andMovePegTo: to andMovePegVia: via andWithNumDisks: 1];
[self movePegFrom: via andMovePegTo: to andMovePegVia: from andWithNumDisks: disks-1];
}
}
@end</syntaxhighlight>
Test code: TowersTest.m:
<syntaxhighlight lang="objc">#import <stdio.h>
#import "TowersOfHanoi.h"
int main( int argc, const char *argv[] ) {
@autoreleasepool {
TowersOfHanoi *tower = [[TowersOfHanoi alloc] init];
int from = 1;
int to = 3;
int via = 2;
int disks = 3;
[tower setPegFrom: from andSetPegTo: to andSetPegVia: via andSetNumDisks: disks];
[tower movePegFrom: from andMovePegTo: to andMovePegVia: via andWithNumDisks: disks];
}
return 0;
}</syntaxhighlight>
=={{header|OCaml}}==
<syntaxhighlight lang="ocaml">let rec hanoi n a b c =
if n <> 0 then begin
hanoi (pred n) a c b;
Printf.printf "Move disk from pole %d to pole %d\n" a b;
hanoi (pred n) c b a
end
let () =
hanoi 4 1 2 3</syntaxhighlight>
=={{header|Octave}}==
<syntaxhighlight lang="octave">function hanoimove(ndisks, from, to, via)
if ( ndisks == 1 )
printf("Move disk from pole %d to pole %d\n", from, to);
else
hanoimove(ndisks-1, from, via, to);
hanoimove(1, from, to, via);
hanoimove(ndisks-1, via, to, from);
endif
endfunction
hanoimove(4, 1, 2, 3);</syntaxhighlight>
=={{header|Oforth}}==
<syntaxhighlight lang="oforth">: move(n, from, to, via)
n 0 > ifTrue: [
move(n 1-, from, via, to)
System.Out "Move disk from " << from << " to " << to << cr
move(n 1-, via, to, from)
] ;
5 $left $middle $right) move </syntaxhighlight>
=={{header|Oz}}==
<syntaxhighlight lang="oz">declare
proc {TowersOfHanoi N From To Via}
if N > 0 then
{TowersOfHanoi N-1 From Via To}
{System.showInfo "Move from "#From#" to "#To}
{TowersOfHanoi N-1 Via To From}
end
end
in
{TowersOfHanoi 4 left middle right}</syntaxhighlight>
=={{header|PARI/GP}}==
{{trans|Python}}
<syntaxhighlight lang="parigp">\\ Towers of Hanoi
\\ 8/19/2016 aev
\\ Where: n - number of disks, sp - start pole, ep - end pole.
HanoiTowers(n,sp,ep)={
if(n!=0,
HanoiTowers(n-1,sp,6-sp-ep);
print("Move disk ", n, " from pole ", sp," to pole ", ep);
HanoiTowers(n-1,6-sp-ep,ep);
);
}
\\ Testing n=3:
HanoiTowers(3,1,3);</syntaxhighlight>
{{Output}}
<pre>
> HanoiTower(3,1,3);
Move disk 1 from pole 1 to pole 3
Move disk 2 from pole 1 to pole 2
Move disk 1 from pole 3 to pole 2
Move disk 3 from pole 1 to pole 3
Move disk 1 from pole 2 to pole 1
Move disk 2 from pole 2 to pole 3
Move disk 1 from pole 1 to pole 3
</pre>
=={{header|Pascal}}==
{{works with|Free Pascal|2.0.4}}
I think it is standard pascal, except for the constant array "strPole". I am not sure if constant arrays are part of the standard. However, as far as I know, they are a "de facto" standard in every compiler.
<syntaxhighlight lang="pascal">program Hanoi;
type
TPole = (tpLeft, tpCenter, tpRight);
const
strPole:array[TPole] of string[6]=('left','center','right');
procedure MoveStack (const Ndisks : integer; const Origin,Destination,Auxiliary:TPole);
begin
if Ndisks >0 then begin
MoveStack(Ndisks - 1, Origin,Auxiliary, Destination );
Writeln('Move disk ',Ndisks ,' from ',strPole[Origin],' to ',strPole[Destination]);
MoveStack(Ndisks - 1, Auxiliary, Destination, origin);
end;
end;
begin
MoveStack(4,tpLeft,tpCenter,tpRight);
end.</syntaxhighlight>
A little longer, but clearer for my taste
<syntaxhighlight lang="pascal">program Hanoi;
type
TPole = (tpLeft, tpCenter, tpRight);
const
strPole:array[TPole] of string[6]=('left','center','right');
procedure MoveOneDisk(const DiskNum:integer; const Origin,Destination:TPole);
begin
Writeln('Move disk ',DiskNum,' from ',strPole[Origin],' to ',strPole[Destination]);
end;
procedure MoveStack (const Ndisks : integer; const Origin,Destination,Auxiliary:TPole);
begin
if Ndisks =1 then
MoveOneDisk(1,origin,Destination)
else begin
MoveStack(Ndisks - 1, Origin,Auxiliary, Destination );
MoveOneDisk(Ndisks,origin,Destination);
MoveStack(Ndisks - 1, Auxiliary, Destination, origin);
end;
end;
begin
MoveStack(4,tpLeft,tpCenter,tpRight);
end.</syntaxhighlight>
=={{header|Perl}}==
<syntaxhighlight lang="perl">sub hanoi {
my ($n, $from, $to, $via) = (@_, 1, 2, 3);
if ($n == 1) {
print "Move disk from pole $from to pole $to.\n";
} else {
hanoi($n - 1, $from, $via, $to);
hanoi(1, $from, $to, $via);
hanoi($n - 1, $via, $to, $from);
};
};</syntaxhighlight>
=={{header|Phix}}==
<!--<syntaxhighlight lang="phix">(phixonline)-->
<span style="color: #008080;">constant</span> <span style="color: #000000;">poles</span> <span style="color: #0000FF;">=</span> <span style="color: #0000FF;">{</span><span style="color: #008000;">"left"</span><span style="color: #0000FF;">,</span><span style="color: #008000;">"middle"</span><span style="color: #0000FF;">,</span><span style="color: #008000;">"right"</span><span style="color: #0000FF;">}</span>
<span style="color: #008080;">enum</span> <span style="color: #000000;">left</span><span style="color: #0000FF;">,</span> <span style="color: #000000;">middle</span><span style="color: #0000FF;">,</span> <span style="color: #000000;">right</span>
<span style="color: #004080;">sequence</span> <span style="color: #000000;">disks</span>
<span style="color: #004080;">integer</span> <span style="color: #000000;">moves</span>
<span style="color: #008080;">procedure</span> <span style="color: #000000;">showpegs</span><span style="color: #0000FF;">(</span><span style="color: #004080;">integer</span> <span style="color: #000000;">src</span><span style="color: #0000FF;">,</span> <span style="color: #004080;">integer</span> <span style="color: #000000;">dest</span><span style="color: #0000FF;">)</span>
<span style="color: #004080;">string</span> <span style="color: #000000;">desc</span> <span style="color: #0000FF;">=</span> <span style="color: #7060A8;">sprintf</span><span style="color: #0000FF;">(</span><span style="color: #008000;">"%s to %s:"</span><span style="color: #0000FF;">,{</span><span style="color: #000000;">poles</span><span style="color: #0000FF;">[</span><span style="color: #000000;">src</span><span style="color: #0000FF;">],</span><span style="color: #000000;">poles</span><span style="color: #0000FF;">[</span><span style="color: #000000;">dest</span><span style="color: #0000FF;">]})</span>
<span style="color: #000000;">disks</span><span style="color: #0000FF;">[</span><span style="color: #000000;">dest</span><span style="color: #0000FF;">]</span> <span style="color: #0000FF;">&=</span> <span style="color: #000000;">disks</span><span style="color: #0000FF;">[</span><span style="color: #000000;">src</span><span style="color: #0000FF;">][$]</span>
<span style="color: #000000;">disks</span><span style="color: #0000FF;">[</span><span style="color: #000000;">src</span><span style="color: #0000FF;">]</span> <span style="color: #0000FF;">=</span> <span style="color: #000000;">disks</span><span style="color: #0000FF;">[</span><span style="color: #000000;">src</span><span style="color: #0000FF;">][</span><span style="color: #000000;">1</span><span style="color: #0000FF;">..$-</span><span style="color: #000000;">1</span><span style="color: #0000FF;">]</span>
<span style="color: #008080;">for</span> <span style="color: #000000;">i</span><span style="color: #0000FF;">=</span><span style="color: #000000;">1</span> <span style="color: #008080;">to</span> <span style="color: #7060A8;">length</span><span style="color: #0000FF;">(</span><span style="color: #000000;">disks</span><span style="color: #0000FF;">)</span> <span style="color: #008080;">do</span>
<span style="color: #7060A8;">printf</span><span style="color: #0000FF;">(</span><span style="color: #000000;">1</span><span style="color: #0000FF;">,</span><span style="color: #008000;">"%-16s | %s\n"</span><span style="color: #0000FF;">,{</span><span style="color: #000000;">desc</span><span style="color: #0000FF;">,</span><span style="color: #7060A8;">join</span><span style="color: #0000FF;">(</span><span style="color: #7060A8;">sq_add</span><span style="color: #0000FF;">(</span><span style="color: #000000;">disks</span><span style="color: #0000FF;">[</span><span style="color: #000000;">i</span><span style="color: #0000FF;">],</span><span style="color: #008000;">'0'</span><span style="color: #0000FF;">),</span><span style="color: #008000;">' '</span><span style="color: #0000FF;">)})</span>
<span style="color: #000000;">desc</span> <span style="color: #0000FF;">=</span> <span style="color: #008000;">""</span>
<span style="color: #008080;">end</span> <span style="color: #008080;">for</span>
<span style="color: #7060A8;">printf</span><span style="color: #0000FF;">(</span><span style="color: #000000;">1</span><span style="color: #0000FF;">,</span><span style="color: #008000;">"\n"</span><span style="color: #0000FF;">)</span>
<span style="color: #000000;">moves</span> <span style="color: #0000FF;">+=</span> <span style="color: #000000;">1</span>
<span style="color: #008080;">end</span> <span style="color: #008080;">procedure</span>
<span style="color: #008080;">procedure</span> <span style="color: #000000;">hanoir</span><span style="color: #0000FF;">(</span><span style="color: #004080;">integer</span> <span style="color: #000000;">n</span><span style="color: #0000FF;">,</span> <span style="color: #000000;">src</span><span style="color: #0000FF;">=</span><span style="color: #000000;">left</span><span style="color: #0000FF;">,</span> <span style="color: #000000;">dest</span><span style="color: #0000FF;">=</span><span style="color: #000000;">right</span><span style="color: #0000FF;">,</span> <span style="color: #000000;">via</span><span style="color: #0000FF;">=</span><span style="color: #000000;">middle</span><span style="color: #0000FF;">)</span>
<span style="color: #008080;">if</span> <span style="color: #000000;">n</span><span style="color: #0000FF;">></span><span style="color: #000000;">0</span> <span style="color: #008080;">then</span>
<span style="color: #000000;">hanoir</span><span style="color: #0000FF;">(</span><span style="color: #000000;">n</span><span style="color: #0000FF;">-</span><span style="color: #000000;">1</span><span style="color: #0000FF;">,</span> <span style="color: #000000;">src</span><span style="color: #0000FF;">,</span> <span style="color: #000000;">via</span><span style="color: #0000FF;">,</span> <span style="color: #000000;">dest</span><span style="color: #0000FF;">)</span>
<span style="color: #000000;">showpegs</span><span style="color: #0000FF;">(</span><span style="color: #000000;">src</span><span style="color: #0000FF;">,</span><span style="color: #000000;">dest</span><span style="color: #0000FF;">)</span>
<span style="color: #000000;">hanoir</span><span style="color: #0000FF;">(</span><span style="color: #000000;">n</span><span style="color: #0000FF;">-</span><span style="color: #000000;">1</span><span style="color: #0000FF;">,</span> <span style="color: #000000;">via</span><span style="color: #0000FF;">,</span> <span style="color: #000000;">dest</span><span style="color: #0000FF;">,</span> <span style="color: #000000;">src</span><span style="color: #0000FF;">)</span>
<span style="color: #008080;">end</span> <span style="color: #008080;">if</span>
<span style="color: #008080;">end</span> <span style="color: #008080;">procedure</span>
<span style="color: #008080;">procedure</span> <span style="color: #000000;">hanoi</span><span style="color: #0000FF;">(</span><span style="color: #004080;">integer</span> <span style="color: #000000;">n</span><span style="color: #0000FF;">)</span>
<span style="color: #000000;">disks</span> <span style="color: #0000FF;">=</span> <span style="color: #0000FF;">{</span><span style="color: #7060A8;">reverse</span><span style="color: #0000FF;">(</span><span style="color: #7060A8;">tagset</span><span style="color: #0000FF;">(</span><span style="color: #000000;">n</span><span style="color: #0000FF;">)),{},{}}</span>
<span style="color: #000000;">moves</span> <span style="color: #0000FF;">=</span> <span style="color: #000000;">0</span>
<span style="color: #000000;">hanoir</span><span style="color: #0000FF;">(</span><span style="color: #000000;">n</span><span style="color: #0000FF;">)</span>
<span style="color: #7060A8;">printf</span><span style="color: #0000FF;">(</span><span style="color: #000000;">1</span><span style="color: #0000FF;">,</span><span style="color: #008000;">"completed in %d moves\n"</span><span style="color: #0000FF;">,{</span><span style="color: #000000;">moves</span><span style="color: #0000FF;">})</span>
<span style="color: #008080;">end</span> <span style="color: #008080;">procedure</span>
<span style="color: #000000;">hanoi</span><span style="color: #0000FF;">(</span><span style="color: #000000;">3</span><span style="color: #0000FF;">)</span> <span style="color: #000080;font-style:italic;">-- (output of 4,5,6 also shown)</span>
<!--</syntaxhighlight>-->
{{Out}}
<pre style="float:left">
left to right: | 3 2
|
| 1
left to middle: | 3
| 2
| 1
right to middle: | 3
| 2 1
|
left to right: |
| 2 1
| 3
middle to left: | 1
| 2
| 3
middle to right: | 1
|
| 3 2
left to right: |
|
| 3 2 1
completed in 7 moves
</pre>
<pre style="float:left">
left to middle: | 4 3 2
| 1
|
left to right: | 4 3
| 1
| 2
middle to right: | 4 3
|
| 2 1
...
left to middle: | 2
| 1
| 4 3
left to right: |
| 1
| 4 3 2
middle to right: |
|
| 4 3 2 1
completed in 15 moves
</pre>
<pre style="float:left">
left to right: | 5 4 3 2
|
| 1
left to middle: | 5 4 3
| 2
| 1
right to middle: | 5 4 3
| 2 1
|
...
middle to left: | 1
| 2
| 5 4 3
middle to right: | 1
|
| 5 4 3 2
left to right: |
|
| 5 4 3 2 1
completed in 31 moves
</pre>
<pre>
left to middle: | 6 5 4 3 2
| 1
|
left to right: | 6 5 4 3
| 1
| 2
middle to right: | 6 5 4 3
|
| 2 1
...
left to middle: | 2
| 1
| 6 5 4 3
left to right: |
| 1
| 6 5 4 3 2
middle to right: |
|
| 6 5 4 3 2 1
completed in 63 moves
</pre>
=={{header|PHL}}==
{{trans|C}}
<syntaxhighlight lang="phl">module hanoi;
extern printf;
@Void move(@Integer n, @Integer from, @Integer to, @Integer via) [
if (n > 0) {
move(n - 1, from, via, to);
printf("Move disk from pole %d to pole %d\n", from, to);
move(n - 1, via, to, from);
}
]
@Integer main [
move(4, 1,2,3);
return 0;
]</syntaxhighlight>
=={{header|PHP}}==
{{trans|Java}}
<syntaxhighlight lang="php">function move($n,$from,$to,$via) {
if ($n === 1) {
print("Move disk from pole $from to pole $to");
} else {
move($n-1,$from,$via,$to);
move(1,$from,$to,$via);
move($n-1,$via,$to,$from);
}
}</syntaxhighlight>
=={{header|Picat}}==
<syntaxhighlight lang="picat">main =>
hanoi(3, left, center, right).
hanoi(0, _From, _To, _Via) => true.
hanoi(N, From, To, Via) =>
hanoi(N - 1, From, Via, To),
printf("Move disk %w from pole %w to pole %w\n", N, From, To),
hanoi(N - 1, Via, To, From).
</syntaxhighlight>
{{out}}
<pre>
Move disk 1 from pole left to pole center
Move disk 2 from pole left to pole right
Move disk 1 from pole center to pole right
Move disk 3 from pole left to pole center
Move disk 1 from pole right to pole left
Move disk 2 from pole right to pole center
Move disk 1 from pole left to pole center
count=7, theoretical=7</pre>
===Fast counting===
<syntaxhighlight lang="picat">main =>
hanoi(64).
hanoi(N) =>
printf("N=%d\n", N),
Count = move(N, left, center, right) ,
printf("count=%w, theoretical=%w\n", Count, 2**N-1).
table
move(0, _From, _To, _Via) = 0.
move(N, From, To, Via) = Count =>
Count1 = move(N - 1, From, Via, To),
Count2 = move(N - 1, Via, To, From),
Count = Count1+Count2+1.
</syntaxhighlight>
{{out}}
<pre>
N=64
count=18446744073709551615, theoretical=18446744073709551615</pre>
=={{header|PicoLisp}}==
<syntaxhighlight lang="picolisp">(de move (N A B C) # Use: (move 3 'left 'center 'right)
(unless (=0 N)
(move (dec N) A C B)
(println 'Move 'disk 'from A 'to B)
(move (dec N) C B A) ) )</syntaxhighlight>
=={{header|PL/I}}==
{{trans|Fortran}}
<syntaxhighlight lang="pli">tower: proc options (main);
call Move (4,1,2,3);
Move: procedure (ndiscs, from, to, via) recursive;
declare (ndiscs, from, to, via) fixed binary;
if ndiscs = 1 then
put skip edit ('Move disc from pole ', trim(from), ' to pole ',
trim(to) ) (a);
else
do;
call Move (ndiscs-1, from, via, to);
call Move (1, from, to, via);
call Move (ndiscs-1, via, to, from);
end;
end Move;
end tower;</syntaxhighlight>
=={{header|PL/M}}==
{{Trans|Tiny BASIC}}
Iterative solution as PL/M doesn't do recursion.
{{works with|8080 PL/M Compiler}} ... under CP/M (or an emulator)
<syntaxhighlight lang="pli">100H: /* ITERATIVE TOWERS OF HANOI; TRANSLATED FROM TINY BASIC (VIA ALGOL W) */
/* CP/M BDOS SYSTEM CALL */
BDOS: PROCEDURE( FN, ARG ); DECLARE FN BYTE, ARG ADDRESS; GOTO 5; END;
/* I/O ROUTINES */
PR$CHAR: PROCEDURE( C ); DECLARE C BYTE; CALL BDOS( 2, C ); END;
PR$STRING: PROCEDURE( S ); DECLARE S ADDRESS; CALL BDOS( 9, S ); END;
DECLARE ( D, N, X, S, T ) ADDRESS;
/* FIXED NUMBER OF DISCS: 4 */
N = 1;
DO D = 1 TO 4;
N = N + N;
END;
DO X = 1 TO N - 1;
/* AS IN ALGOL W, WE CAN USE PL/M'S BIT ABD MOD OPERATORS */
S = ( X AND ( X - 1 ) ) MOD 3;
T = ( ( X OR ( X - 1 ) ) + 1 ) MOD 3;
CALL PR$STRING( .'MOVE DISC ON PEG $' );
CALL PR$CHAR( '1' + S );
CALL PR$STRING( .' TO PEG $' );
CALL PR$CHAR( '1' + T );
CALL PR$STRING( .( 0DH, 0AH, '$' ) );
END;
EOF</syntaxhighlight>
{{out}}
<pre>
MOVE DISC ON PEG 1 TO PEG 3
MOVE DISC ON PEG 1 TO PEG 2
MOVE DISC ON PEG 3 TO PEG 2
MOVE DISC ON PEG 1 TO PEG 3
MOVE DISC ON PEG 2 TO PEG 1
MOVE DISC ON PEG 2 TO PEG 3
MOVE DISC ON PEG 1 TO PEG 3
MOVE DISC ON PEG 1 TO PEG 2
MOVE DISC ON PEG 3 TO PEG 2
MOVE DISC ON PEG 3 TO PEG 1
MOVE DISC ON PEG 2 TO PEG 1
MOVE DISC ON PEG 3 TO PEG 2
MOVE DISC ON PEG 1 TO PEG 3
MOVE DISC ON PEG 1 TO PEG 2
MOVE DISC ON PEG 3 TO PEG 2
</pre>
=={{header|PlainTeX}}==
<syntaxhighlight lang="tex">\newcount\hanoidepth
\def\hanoi#1{%
\hanoidepth = #1
\move abc
}%
\def\move#1#2#3{%
\advance \hanoidepth by -1
\ifnum \hanoidepth > 0
\move #1#3#2
\fi
Move the upper disk from pole #1 to pole #3.\par
\ifnum \hanoidepth > 0
\move#2#1#3
\fi
\advance \hanoidepth by 1
}
\hanoi{5}
\end</syntaxhighlight>
=={{header|Pop11}}==
<syntaxhighlight lang="pop11">define hanoi(n, src, dst, via);
if n > 0 then
hanoi(n - 1, src, via, dst);
'Move disk ' >< n >< ' from ' >< src >< ' to ' >< dst >< '.' =>
hanoi(n - 1, via, dst, src);
endif;
enddefine;
hanoi(4, "left", "middle", "right");</syntaxhighlight>
=={{header|PostScript}}==
A million-page document, each page showing one move.
<syntaxhighlight lang="postscript">%!PS-Adobe-3.0
%%BoundingBox: 0 0 300 300
/plate {
exch 100 mul 50 add exch th mul 10 add moveto
dup s mul neg 2 div 0 rmoveto
dup s mul 0 rlineto
0 th rlineto
s neg mul 0 rlineto
closepath gsave .5 setgray fill grestore 0 setgray stroke
} def
/drawtower {
0 1 2 { /x exch def /y 0 def
tower x get {
dup 0 gt { x y plate /y y 1 add def } {pop} ifelse
} forall
} for showpage
} def
/apop { [ exch aload pop /last exch def ] last } def
/apush{ [ 3 1 roll aload pop counttomark -1 roll ] } def
/hanoi {
0 dict begin /from /mid /to /h 5 -1 2 { -1 roll def } for
h 1 eq {
tower from get apop tower to get apush
tower to 3 -1 roll put
tower from 3 -1 roll put
drawtower
} {
/h h 1 sub def
from to mid h hanoi
from mid to 1 hanoi
mid from to h hanoi
} ifelse
end
} def
/n 12 def
/s 90 n div def
/th 180 n div def
/tower [ [n 1 add -1 2 { } for ] [] [] ] def
drawtower 0 1 2 n hanoi
%%EOF</syntaxhighlight>
=={{header|PowerShell}}==
{{works with|PowerShell|4.0}}
<syntaxhighlight lang="powershell">
function hanoi($n, $a, $b, $c) {
if($n -eq 1) {
"$a -> $c"
} else{
hanoi ($n - 1) $a $c $b
hanoi 1 $a $b $c
hanoi ($n - 1) $b $a $c
}
}
hanoi 3 "A" "B" "C"
</syntaxhighlight>
<b>Output:</b>
<pre>
A -> C
A -> B
C -> B
A -> C
B -> A
B -> C
A -> C
</pre>
=={{header|Prolog}}==
From Programming in Prolog by W.F. Clocksin & C.S. Mellish
<syntaxhighlight lang="prolog">hanoi(N) :- move(N,left,center,right).
move(0,_,_,_) :- !.
move(N,A,B,C) :-
M is N-1,
move(M,A,C,B),
inform(A,B),
move(M,C,B,A).
inform(X,Y) :- write([move,a,disk,from,the,X,pole,to,Y,pole]), nl.</syntaxhighlight>
Using DCGs and separating core logic from IO
<syntaxhighlight lang="prolog">
hanoi(N, Src, Aux, Dest, Moves-NMoves) :-
NMoves is 2^N - 1,
length(Moves, NMoves),
phrase(move(N, Src, Aux, Dest), Moves).
move(1, Src, _, Dest) --> !,
[Src->Dest].
move(2, Src, Aux, Dest) --> !,
[Src->Aux,Src->Dest,Aux->Dest].
move(N, Src, Aux, Dest) -->
{ succ(N0, N) },
move(N0, Src, Dest, Aux),
move(1, Src, Aux, Dest),
move(N0, Aux, Src, Dest).
</syntaxhighlight>
=={{header|PureBasic}}==
Algorithm according to http://en.wikipedia.org/wiki/Towers_of_Hanoi
<syntaxhighlight lang="purebasic">Procedure Hanoi(n, A.s, C.s, B.s)
If n
Hanoi(n-1, A, B, C)
PrintN("Move the plate from "+A+" to "+C)
Hanoi(n-1, B, C, A)
EndIf
EndProcedure</syntaxhighlight>
Full program
<syntaxhighlight lang="purebasic">Procedure Hanoi(n, A.s, C.s, B.s)
If n
Hanoi(n-1, A, B, C)
PrintN("Move the plate from "+A+" to "+C)
Hanoi(n-1, B, C, A)
EndIf
EndProcedure
If OpenConsole()
Define n=3
PrintN("Moving "+Str(n)+" pegs."+#CRLF$)
Hanoi(n,"Left Peg","Middle Peg","Right Peg")
PrintN(#CRLF$+"Press ENTER to exit."): Input()
EndIf</syntaxhighlight>
{{out}}
Moving 3 pegs.
Move the plate from Left Peg to Middle Peg
Move the plate from Left Peg to Right Peg
Move the plate from Middle Peg to Right Peg
Move the plate from Left Peg to Middle Peg
Move the plate from Right Peg to Left Peg
Move the plate from Right Peg to Middle Peg
Move the plate from Left Peg to Middle Peg
Press ENTER to exit.
=={{header|Python}}==
===Recursive===
<syntaxhighlight lang="python">def hanoi(ndisks, startPeg=1, endPeg=3):
if ndisks:
hanoi(ndisks-1, startPeg, 6-startPeg-endPeg)
print(f"Move disk {ndisks} from peg {startPeg} to peg {endPeg}")
hanoi(ndisks-1, 6-startPeg-endPeg, endPeg)
hanoi(4)</syntaxhighlight>
{{out}} for ndisks=2
<pre>
Move disk 1 from peg 1 to peg 2
Move disk 2 from peg 1 to peg 3
Move disk 1 from peg 2 to peg 3
</pre>
Or, separating the definition of the data from its display:
{{Works with|Python|3.7}}
<syntaxhighlight lang="python">'''Towers of Hanoi'''
# hanoi :: Int -> String -> String -> String -> [(String, String)]
def hanoi(n):
'''A list of (from, to) label pairs,
where a, b and c are labels for each of the
three Hanoi tower positions.'''
def go(n, a, b, c):
p = n - 1
return (
go(p, a, c, b) + [(a, b)] + go(p, c, b, a)
) if 0 < n else []
return lambda a: lambda b: lambda c: go(n, a, b, c)
# TEST ----------------------------------------------------
if __name__ == '__main__':
# fromTo :: (String, String) -> String
def fromTo(xy):
'''x -> y'''
x, y = xy
return x.rjust(5, ' ') + ' -> ' + y
print(__doc__ + ':\n\n' + '\n'.join(
map(fromTo, hanoi(4)('left')('right')('mid'))
))</syntaxhighlight>
{{Out}}
<pre>Towers of Hanoi:
left -> mid
left -> right
mid -> right
left -> mid
right -> left
right -> mid
left -> mid
left -> right
mid -> right
mid -> left
right -> left
mid -> right
left -> mid
left -> right
mid -> right</pre>
===Graphic===
Refactoring the version above to recursively generate a simple visualisation:
{{Works with|Python|3.7}}
<syntaxhighlight lang="python">'''Towers of Hanoi'''
from itertools import accumulate, chain, repeat
from inspect import signature
import operator
# hanoi :: Int -> [(Int, Int)]
def hanoi(n):
'''A list of index pairs, representing disk moves
between indexed Hanoi positions.
'''
def go(n, a, b, c):
p = n - 1
return (
go(p, a, c, b) + [(a, b)] + go(p, c, b, a)
) if 0 < n else []
return go(n, 0, 2, 1)
# hanoiState :: ([Int],[Int],[Int], String) -> (Int, Int) ->
# ([Int],[Int],[Int], String)
def hanoiState(tpl, ab):
'''A new Hanoi tower state'''
a, b = ab
xs, ys = tpl[a], tpl[b]
w = 3 * (2 + (2 * max(map(max, filter(len, tpl[:-1])))))
def delta(i):
return tpl[i] if i not in ab else xs[1:] if (
i == a
) else [xs[0]] + ys
tkns = moveName(('left', 'mid', 'right'))(ab)
caption = ' '.join(tkns)
return tuple(map(delta, [0, 1, 2])) + (
(caption if tkns[0] != 'mid' else caption.rjust(w, ' ')),
)
# showHanoi :: ([Int],[Int],[Int], String) -> String
def showHanoi(tpl):
'''Captioned string representation of an updated Hanoi tower state.'''
def fullHeight(n):
return lambda xs: list(repeat('', n - len(xs))) + xs
mul = curry(operator.mul)
lt = curry(operator.lt)
rods = fmap(fmap(mul('__')))(
list(tpl[0:3])
)
h = max(map(len, rods))
w = 2 + max(
map(
compose(max)(fmap(len)),
filter(compose(lt(0))(len), rods)
)
)
xs = fmap(concat)(
transpose(fmap(
compose(fmap(center(w)(' ')))(
fullHeight(h)
)
)(rods))
)
return tpl[3] + '\n\n' + unlines(xs) + '\n' + ('___' * w)
# moveName :: (String, String, String) -> (Int, Int) -> [String]
def moveName(labels):
'''(from, to) index pair represented as an a -> b string.'''
def go(ab):
a, b = ab
return [labels[a], ' to ', labels[b]] if a < b else [
labels[b], ' from ', labels[a]
]
return lambda ab: go(ab)
# TEST ----------------------------------------------------
def main():
'''Visualisation of a Hanoi tower sequence for N discs.
'''
n = 3
print('Hanoi sequence for ' + str(n) + ' disks:\n')
print(unlines(
fmap(showHanoi)(
scanl(hanoiState)(
(enumFromTo(1)(n), [], [], '')
)(hanoi(n))
)
))
# GENERIC -------------------------------------------------
# center :: Int -> Char -> String -> String
def center(n):
'''String s padded with c to approximate centre,
fitting in but not truncated to width n.'''
return lambda c: lambda s: s.center(n, c)
# compose (<<<) :: (b -> c) -> (a -> b) -> a -> c
def compose(g):
'''Right to left function composition.'''
return lambda f: lambda x: g(f(x))
# concat :: [[a]] -> [a]
# concat :: [String] -> String
def concat(xs):
'''The concatenation of all the elements
in a list or iterable.'''
def f(ys):
zs = list(chain(*ys))
return ''.join(zs) if isinstance(ys[0], str) else zs
return (
f(xs) if isinstance(xs, list) else (
chain.from_iterable(xs)
)
) if xs else []
# curry :: ((a, b) -> c) -> a -> b -> c
def curry(f):
'''A curried function derived
from an uncurried function.'''
if 1 < len(signature(f).parameters):
return lambda x: lambda y: f(x, y)
else:
return f
# enumFromTo :: (Int, Int) -> [Int]
def enumFromTo(m):
'''Integer enumeration from m to n.'''
return lambda n: list(range(m, 1 + n))
# fmap :: (a -> b) -> [a] -> [b]
def fmap(f):
'''fmap over a list.
f lifted to a function over a list.
'''
return lambda xs: list(map(f, xs))
# scanl :: (b -> a -> b) -> b -> [a] -> [b]
def scanl(f):
'''scanl is like reduce, but returns a succession of
intermediate values, building from the left.
'''
return lambda a: lambda xs: (
accumulate(chain([a], xs), f)
)
# showLog :: a -> IO String
def showLog(*s):
'''Arguments printed with
intercalated arrows.'''
print(
' -> '.join(map(str, s))
)
# transpose :: Matrix a -> Matrix a
def transpose(m):
'''The rows and columns of the argument transposed.
(The matrix containers and rows can be lists or tuples).
'''
if m:
inner = type(m[0])
z = zip(*m)
return (type(m))(
map(inner, z) if tuple != inner else z
)
else:
return m
# unlines :: [String] -> String
def unlines(xs):
'''A single string derived by the intercalation
of a list of strings with the newline character.
'''
return '\n'.join(xs)
# TEST ----------------------------------------------------
if __name__ == '__main__':
main()</syntaxhighlight>
<pre>Hanoi sequence for 3 disks:
__
____
______
________________________
left to right
____
______ __
________________________
left to mid
______ ____ __
________________________
mid from right
__
______ ____
________________________
left to right
__
____ ______
________________________
left from mid
__ ____ ______
________________________
mid to right
____
__ ______
________________________
left to right
__
____
______
________________________</pre>
==={{libheader|VPython}}===
There is a 3D hanoi-game in the examples that come with VPython,
and at [https://github.com/vpython/visual/blob/master/examples/hanoi.py github].
=={{header|Quackery}}==
<syntaxhighlight lang="quackery"> [ stack ] is rings ( --> [ )
[ rings share
depth share -
8 * times sp
emit sp emit sp
say 'move' cr ] is echomove ( c c --> )
[ dup rings put
depth put
char a char b char c
[ swap decurse
rot 2dup echomove
decurse
swap rot ]
3 times drop
depth release
rings release ] is hanoi ( n --> n )
say 'How to solve a three ring Towers of Hanoi puzzle:' cr cr
3 hanoi cr</syntaxhighlight>
{{out}}
<pre>How to solve a three ring Towers of Hanoi puzzle:
a c move
a b move
c b move
a c move
b a move
b c move
a c move
a b move
c b move
c a move
b a move
c b move
a c move
a b move
c b move
</pre>
=={{header|Quite BASIC}}==
'This is implemented on the Quite BASIC website
'http://www.quitebasic.com/prj/puzzle/towers-of-hanoi/
<syntaxhighlight lang="quite basic">1000 REM Towers of Hanoi
1010 REM Quite BASIC Puzzle Project
1020 CLS
1030 PRINT "Towers of Hanoi"
1040 PRINT
1050 PRINT "This is a recursive solution for seven discs."
1060 PRINT
1070 PRINT "See the REM statements in the program if you didn't think that recursion was possible in classic BASIC!"
1080 REM Yep, recursive GOSUB calls works in Quite BASIC!
1090 REM However, to actually write useful recursive algorithms, it helps to have variable scoping and parameters to subroutines -- something classic BASIC is lacking. In this case we have only one "parameter" -- the variable N. And subroutines are always called with N-1. This is lucky for us because we can keep track of the value by decrementing it when we enter subroutines and incrementing it back when we exit.
1100 REM If we had subroutine parameters we could have written a single subroutine for moving discs from peg P to peg Q where P and Q were subroutine parameters, but no such luck. Instead we have to write six different subroutines for moving from peg to peg. See Subroutines 4000, 5000, 6000, 7000, 8000, and 9000.
1110 REM ===============================
2000 REM A, B, and C are arrays holding the discs
2010 REM We refer to the corresponding pegs as peg A, B, and C
2020 ARRAY A
2030 ARRAY B
2040 ARRAY C
2050 REM Fill peg A with seven discs
2060 FOR I = 0 TO 6
2070 LET A[I] = 7 - I
2080 NEXT I
2090 REM X, Y, Z hold the number of discs on pegs A, B, and C
2100 LET X = 7
2110 LET Y = 0
2120 LET Z = 0
2130 REM Disc colors
2140 ARRAY P
2150 LET P[1] = "cyan"
2160 LET P[2] = "blue"
2170 LET P[3] = "green"
2180 LET P[4] = "yellow"
2190 LET P[5] = "magenta"
2200 LET P[6] = "orange"
2210 LET P[7] = "red"
2220 REM Draw initial position -- all discs on the A peg
2230 FOR I = 0 TO 6
2240 FOR J = 8 - A[I] TO 8 + A[I]
2250 PLOT J, I, P[A[I]]
2260 NEXT J
2270 NEXT I
2280 REM N is the number of discs to move
2290 LET N = 7
2320 REM Move all discs from peg A to peg B
2310 GOSUB 6000
2320 END
3000 REM The subroutines 3400, 3500, 3600, 3700, 3800, 3900
3010 REM handle the drawing of the discs on the canvas as we
3020 REM move discs from one peg to another.
3030 REM These subroutines also update the variables X, Y, and Z
3040 REM which hold the number of discs on each peg.
3050 REM ==============================
3400 REM Subroutine -- Remove disc from peg A
3410 LET X = X - 1
3420 FOR I = 8 - A[X] TO 8 + A[X]
3430 PLOT I, X, "gray"
3440 NEXT I
3450 RETURN
3500 REM Subroutine -- Add disc to peg A
3510 FOR I = 8 - A[X] TO 8 + A[X]
3520 PLOT I, X, P[A[X]]
3530 NEXT I
3540 LET X = X + 1
3550 PAUSE 400 * (5 - LEVEL) + 10
3560 RETURN
3600 REM Subroutine -- Remove disc from peg B
3610 LET Y = Y - 1
3620 FOR I = 24 - B[Y] TO 24 + B[Y]
3630 PLOT I, Y, "gray"
3640 NEXT I
3650 RETURN
3700 REM Subroutine -- Add disc to peg B
3710 FOR I = 24 - B[Y] TO 24 + B[Y]
3720 PLOT I, Y, P[B[Y]]
3730 NEXT I
3740 LET Y = Y + 1
3750 PAUSE 400 * (5 - LEVEL) + 10
3760 RETURN
3800 REM Subroutine -- Remove disc from peg C
3810 LET Z = Z - 1
3820 FOR I = 40 - C[Z] TO 40 + C[Z]
3830 PLOT I, Z, "gray"
3840 NEXT I
3850 RETURN
3900 REM Subroutine -- Add disc to peg C
3910 FOR I = 40 - C[Z] TO 40 + C[Z]
3920 PLOT I, Z, P[C[Z]]
3930 NEXT I
3940 LET Z = Z + 1
3950 PAUSE 400 * (5 - LEVEL) + 10
3960 RETURN
4000 REM ======================================
4010 REM Recursive Subroutine -- move N discs from peg B to peg A
4020 REM First move N-1 discs from peg B to peg C
4030 LET N = N - 1
4040 IF N <> 0 THEN GOSUB 9000
4050 REM Then move one disc from peg B to peg A
4060 GOSUB 3600
4070 LET A[X] = B[Y]
4080 GOSUB 3500
4090 REM And finally move N-1 discs from peg C to peg A
4100 IF N <> 0 THEN GOSUB 5000
4110 REM Restore N before returning
4120 LET N = N + 1
4130 RETURN
5000 REM ======================================
5010 REM Recursive Subroutine -- Move N discs from peg C to peg A
5020 REM First move N-1 discs from peg C to peg B
5030 LET N = N - 1
5040 IF N <> 0 THEN GOSUB 8000
5050 REM Then move one disc from peg C to peg A
5060 GOSUB 3800
5070 LET A[X] = C[Z]
5080 GOSUB 3500
5090 REM And finally move N-1 discs from peg B to peg A
5100 IF N <> 0 THEN GOSUB 4000
5120 REM Restore N before returning
5130 LET N = N + 1
5140 RETURN
6000 REM ======================================
6000 REM Recursive Subroutine -- Move N discs from peg A to peg B
6010 REM First move N-1 discs from peg A to peg C
6020 LET N = N - 1
6030 IF N <> 0 THEN GOSUB 7000
6040 REM Then move one disc from peg A to peg B
6050 GOSUB 3400
6060 LET B[Y] = A[X]
6070 GOSUB 3700
6090 REM And finally move N-1 discs from peg C to peg B
6100 IF N <> 0 THEN GOSUB 8000
6110 REM Restore N before returning
6120 LET N = N + 1
6130 RETURN
7000 REM ======================================
7010 REM Recursive Subroutine -- Move N discs from peg A to peg C
7020 REM First move N-1 discs from peg A to peg B
7030 LET N = N - 1
7040 IF N <> 0 THEN GOSUB 6000
7050 REM Then move one disc from peg A to peg C
7060 GOSUB 3400
7070 LET C[Z] = A[X]
7080 GOSUB 3900
7090 REM And finally move N-1 discs from peg B to peg C
7100 IF N <> 0 THEN GOSUB 9000
7110 REM Restore N before returning
7120 LET N = N + 1
7130 RETURN
8000 REM ======================================
8010 REM Recursive Subroutine -- Move N discs from peg C to peg B
8020 REM First move N-1 discs from peg C to peg A
8030 LET N = N - 1
8040 IF N <> 0 THEN GOSUB 5000
8050 REM Then move one disc from peg C to peg B
8060 GOSUB 3800
8070 LET B[Y] = C[Z]
8080 GOSUB 3700
8090 REM And finally move N-1 discs from peg A to peg B
8100 IF N <> 0 THEN GOSUB 6000
8110 REM Restore N before returning
8120 LET N = N + 1
8130 RETURN
9000 REM ======================================
9010 REM Recursive Subroutine -- Move N discs from peg B to peg C
9020 REM First move N-1 discs from peg B to peg A
9030 LET N = N - 1
9040 IF N <> 0 THEN GOSUB 4000
9050 REM Then move one disc from peg B to peg C
9060 GOSUB 3600
9070 LET C[Z] = B[Y]
9080 GOSUB 3900
9090 REM And finally move N-1 discs from peg A to peg C
9100 IF N <> 0 THEN GOSUB 7000
9110 REM Restore N before returning
9120 LET N = N + 1
9130 RETURN</syntaxhighlight>
=={{header|R}}==
{{trans|Octave}}
<syntaxhighlight lang="rsplus">hanoimove <- function(ndisks, from, to, via) {
if (ndisks == 1) {
cat("move disk from", from, "to", to, "\n")
} else {
hanoimove(ndisks - 1, from, via, to)
hanoimove(1, from, to, via)
hanoimove(ndisks - 1, via, to, from)
}
}
hanoimove(4, 1, 2, 3)</syntaxhighlight>
=={{header|Racket}}==
<syntaxhighlight lang="racket">
#lang racket
(define (hanoi n a b c)
(when (> n 0)
(hanoi (- n 1) a c b)
(printf "Move ~a to ~a\n" a b)
(hanoi (- n 1) c b a)))
(hanoi 4 'left 'middle 'right)
</syntaxhighlight>
=={{header|Raku}}==
(formerly Perl 6)
<syntaxhighlight lang="raku" line>subset Peg of Int where 1|2|3;
multi hanoi (0, Peg $a, Peg $b, Peg $c) { }
multi hanoi (Int $n, Peg $a = 1, Peg $b = 2, Peg $c = 3) {
hanoi $n - 1, $a, $c, $b;
say "Move $a to $b.";
hanoi $n - 1, $c, $b, $a;
}</syntaxhighlight>
=={{header|Rascal}}==
{{trans|Python}}
<syntaxhighlight lang="rascal">public void hanoi(ndisks, startPeg, endPeg){
if(ndisks>0){
hanoi(ndisks-1, startPeg, 6 - startPeg - endPeg);
println("Move disk <ndisks> from peg <startPeg> to peg <endPeg>");
hanoi(ndisks-1, 6 - startPeg - endPeg, endPeg);
}
}</syntaxhighlight>
{{out}}
<syntaxhighlight lang="rascal">rascal>hanoi(4,1,3)
Move disk 1 from peg 1 to peg 2
Move disk 2 from peg 1 to peg 3
Move disk 1 from peg 2 to peg 3
Move disk 3 from peg 1 to peg 2
Move disk 1 from peg 3 to peg 1
Move disk 2 from peg 3 to peg 2
Move disk 1 from peg 1 to peg 2
Move disk 4 from peg 1 to peg 3
Move disk 1 from peg 2 to peg 3
Move disk 2 from peg 2 to peg 1
Move disk 1 from peg 3 to peg 1
Move disk 3 from peg 2 to peg 3
Move disk 1 from peg 1 to peg 2
Move disk 2 from peg 1 to peg 3
Move disk 1 from peg 2 to peg 3
ok</syntaxhighlight>
=={{header|Raven}}==
{{trans|Python}}
<syntaxhighlight lang="raven">define hanoi use ndisks, startpeg, endpeg
ndisks 0 > if
6 startpeg - endpeg - startpeg ndisks 1 - hanoi
endpeg startpeg ndisks "Move disk %d from peg %d to peg %d\n" print
endpeg 6 startpeg - endpeg - ndisks 1 - hanoi
define dohanoi use ndisks
# startpeg=1, endpeg=3
3 1 ndisks hanoi
# 4 disks
4 dohanoi
</syntaxhighlight>
{{out}}
<pre>raven hanoi.rv
Move disk 1 from peg 1 to peg 2
Move disk 2 from peg 1 to peg 3
Move disk 1 from peg 2 to peg 3
Move disk 3 from peg 1 to peg 2
Move disk 1 from peg 3 to peg 1
Move disk 2 from peg 3 to peg 2
Move disk 1 from peg 1 to peg 2
Move disk 4 from peg 1 to peg 3
Move disk 1 from peg 2 to peg 3
Move disk 2 from peg 2 to peg 1
Move disk 1 from peg 3 to peg 1
Move disk 3 from peg 2 to peg 3
Move disk 1 from peg 1 to peg 2
Move disk 2 from peg 1 to peg 3
Move disk 1 from peg 2 to peg 3
</pre>
=={{header|REBOL}}==
<syntaxhighlight lang="rebol">REBOL [
Title: "Towers of Hanoi"
URL: http://rosettacode.org/wiki/Towers_of_Hanoi
]
hanoi: func [
{Begin moving the golden disks from one pole to the next.
Note: when last disk moved, the world will end.}
disks [integer!] "Number of discs on starting pole."
/poles "Name poles."
from to via
][
if disks = 0 [return]
if not poles [from: 'left to: 'middle via: 'right]
hanoi/poles disks - 1 from via to
print [from "->" to]
hanoi/poles disks - 1 via to from
]
hanoi 4</syntaxhighlight>
{{out}}
<pre>left -> right
left -> middle
right -> middle
left -> right
middle -> left
middle -> right
left -> right
left -> middle
right -> middle
right -> left
middle -> left
right -> middle
left -> right
left -> middle
right -> middle</pre>
=={{header|Refal}}==
<syntaxhighlight lang="refal">$ENTRY Go {
= <Move 4 1 2 3>;
};
Move {
0 e.X = ;
s.N s.Src s.Via s.Dest, <- s.N 1>: s.Next =
<Move s.Next s.Src s.Dest s.Via>
<Prout "Move disk from pole" s.Src "to pole" s.Dest>
<Move s.Next s.Via s.Src s.Dest>;
};</syntaxhighlight>
{{out}}
<pre>Move disk from pole 1 to pole 2
Move disk from pole 1 to pole 3
Move disk from pole 2 to pole 3
Move disk from pole 1 to pole 2
Move disk from pole 3 to pole 1
Move disk from pole 3 to pole 2
Move disk from pole 1 to pole 2
Move disk from pole 1 to pole 3
Move disk from pole 2 to pole 3
Move disk from pole 2 to pole 1
Move disk from pole 3 to pole 1
Move disk from pole 2 to pole 3
Move disk from pole 1 to pole 2
Move disk from pole 1 to pole 3
Move disk from pole 2 to pole 3</pre>
=={{header|Retro}}==
<syntaxhighlight lang="retro">[[User:Wodan58|Wodan58]] ([[User talk:Wodan58|talk]])
{ 'Num 'From 'To 'Via } [ var ] a:for-each
:set !Via !To !From !Num ;
:display @To @From 'Move_a_ring_from_%n_to_%n\n s:format s:put ;
:hanoi (num,from,to,via-)
set @Num n:-zero?
[ @Num @From @To @Via
@Num n:dec @From @Via @To hanoi set display
@Num n:dec @Via @To @From hanoi ] if ;
#3 #1 #3 #2 hanoi nl
[[User:Wodan58|Wodan58]] ([[User talk:Wodan58|talk]])</syntaxhighlight>
=={{header|REXX}}==
===simple text moves===
<syntaxhighlight lang="rexx">/*REXX program displays the moves to solve the Tower of Hanoi (with N disks). */
parse arg N . /*get optional number of disks from CL.*/
if N=='' | N=="," then N=3 /*Not specified? Then use the default.*/
#= 0 /*#: the number of disk moves (so far)*/
z= 2**N - 1 /*Z: " " " minimum # of moves.*/
call mov 1, 3, N /*move the top disk, then recurse ··· */
say /* [↓] Display the minimum # of moves.*/
say 'The minimum number of moves to solve a ' N"─disk Tower of Hanoi is " z
exit /*stick a fork in it, we're all done. */
/*──────────────────────────────────────────────────────────────────────────────────────*/
mov: procedure expose # z; parse arg @1,@2,@3; L= length(z)
if @3==1 then do; #= # + 1 /*bump the (disk) move counter by one. */
say 'step' right(#, L)": move disk on tower" @1 '───►' @2
end
else do; call mov @1, 6 -@1 -@2, @3 -1
call mov @1, @2, 1
call mov 6 - @1 - @2, @2, @3 -1
end
return /* [↑] this subroutine uses recursion.*/</syntaxhighlight>
{{out|output|text= when using the default input:}}
<pre>
step 1: move disk on tower 1 ───► 3
step 2: move disk on tower 1 ───► 2
step 3: move disk on tower 3 ───► 2
step 4: move disk on tower 1 ───► 3
step 5: move disk on tower 2 ───► 1
step 6: move disk on tower 2 ───► 3
step 7: move disk on tower 1 ───► 3
The minimum number of moves to solve a 3-disk Tower of Hanoi is 7
</pre>
'''output''' when the following was entered (to solve with four disks): <tt> 4 </tt>
<pre>
step 1: move disk on tower 1 ───► 2
step 2: move disk on tower 1 ───► 3
step 3: move disk on tower 2 ───► 3
step 4: move disk on tower 1 ───► 2
step 5: move disk on tower 3 ───► 1
step 6: move disk on tower 3 ───► 2
step 7: move disk on tower 1 ───► 2
step 8: move disk on tower 1 ───► 3
step 9: move disk on tower 2 ───► 3
step 10: move disk on tower 2 ───► 1
step 11: move disk on tower 3 ───► 1
step 12: move disk on tower 2 ───► 3
step 13: move disk on tower 1 ───► 2
step 14: move disk on tower 1 ───► 3
step 15: move disk on tower 2 ───► 3
The minimum number of moves to solve a 4-disk Tower of Hanoi is 15
</pre>
===pictorial moves===
This REXX version pictorially shows (via ASCII art) the moves for solving the Town of Hanoi.
Quite a bit of code has been dedicated to showing a "picture" of the towers with the disks, and the movement of the disk (for each move). "Coloring" of the disks is attempted with dithering.
In addition, it shows each move in a count<u>down</u> manner (the last move is marked as #1).
It may not be obvious from the pictorial display of the moves, but whenever a disk is moved from one tower to another, it is always the top disk that is moved (to the target tower).
Also, since the pictorial showing of the moves may be voluminous (especially for a larger number of disks), the move counter is started with the maximum and is the count shown is decremented so the viewer can see how many moves are left to display.
<syntaxhighlight lang="rexx">/*REXX program displays the moves to solve the Tower of Hanoi (with N disks). */
parse arg N . /*get optional number of disks from CL.*/
if N=='' | N=="," then N=3 /*Not specified? Then use the default.*/
sw= 80; wp= sw%3 - 1; blanks= left('', wp) /*define some default REXX variables. */
c.1= sw % 3 % 2 /* [↑] SW: assume default Screen Width*/
c.2= sw % 2 - 1 /* ◄─── C.1 C.2 C.2 are the positions*/
c.3= sw - 2 - c.1 /* of the 3 columns.*/
#= 0; z= 2**N - 1; moveK= z /*#moves; min# of moves; where to move.*/
@abc= 'abcdefghijklmnopqrstuvwxyN' /*dithering chars when many disks used.*/
ebcdic= ('f2'x==2) /*determine if EBCDIC or ASCII machine.*/
if ebcdic then do; bar= 'bf'x; ar= "df"x; dither= 'db9f9caf'x; down= "9a"x
tr= 'bc'x; bl= "ab"x; br= 'bb'x; vert= "fa"x; tl= 'ac'x
end
else do; bar= 'c4'x; ar= "10"x; dither= 'b0b1b2db'x; down= "19"x
tr= 'bf'x; bl= "c0"x; br= 'd9'x; vert= "b3"x; tl= 'da'x
end
verts= vert || vert; Tcorners= tl || tr; box = left(dither, 1)
downs= down || down; Bcorners= bl || br; boxChars= dither || @abc
$.= 0; $.1= N; k= N; kk= k + k
do j=1 for N; @.3.j= blanks; @.2.j= blanks; @.1.j= center( copies(box, kk), wp)
if N<=length(boxChars) then @.1.j= translate( @.1.j, , substr( boxChars, kk%2, 1), box)
kk= kk - 2
end /*j*/ /*populate the tower of Hanoi spindles.*/
call showTowers; call mov 1,3,N; say
say 'The minimum number of moves to solve a ' N"-disk Tower of Hanoi is " z
exit /*stick a fork in it, we're all done. */
/*──────────────────────────────────────────────────────────────────────────────────────*/
dsk: parse arg from dest; #= # + 1; pp=
if from==1 then do; pp= overlay(bl, pp, c.1)
pp= overlay(bar, pp, c.1+1, c.dest-c.1-1, bar) || tr
end
if from==2 then do
if dest==1 then do; pp= overlay(tl, pp, c.1)
pp= overlay(bar, pp, c.1+1, c.2-c.1-1,bar)||br
end
if dest==3 then do; pp= overlay(bl, pp, c.2)
pp= overlay(bar, pp, c.2+1, c.3-c.2-1,bar)||tr
end
end
if from==3 then do; pp= overlay(br, pp, c.3)
pp= overlay(bar, pp, c.dest+1, c.3-c.dest-1, bar)
pp= overlay(tl, pp, c.dest)
end
say translate(pp, downs, Bcorners || Tcorners || bar); say overlay(moveK, pp, 1)
say translate(pp, verts, Tcorners || Bcorners || bar)
say translate(pp, downs, Tcorners || Bcorners || bar); moveK= moveK - 1
$.from= $.from - 1; $.dest= $.dest + 1; _f= $.from + 1; _t= $.dest
@.dest._t= @.from._f; @.from._f= blanks; call showTowers
return
/*──────────────────────────────────────────────────────────────────────────────────────*/
mov: if arg(3)==1 then call dsk arg(1) arg(2)
else do; call mov arg(1), 6 -arg(1) -arg(2), arg(3) -1
call mov arg(1), arg(2), 1
call mov 6 -arg(1) -arg(2), arg(2), arg(3) -1
end /* [↑] The MOV subroutine is recursive, */
return /*it uses no variables, is uses BIFs instead*/
/*──────────────────────────────────────────────────────────────────────────────────────*/
showTowers: do j=N by -1 for N; _=@.1.j @.2.j @.3.j; if _\='' then say _; end; return</syntaxhighlight>
{{out|output|text= when using the default input:}}
<pre>
░░
▒▒▒▒
▓▓▓▓▓▓
↓
7 └───────────────────────────────────────────────────┐
│
↓
▒▒▒▒
▓▓▓▓▓▓ ░░
↓
6 └─────────────────────────┐
│
↓
▓▓▓▓▓▓ ▒▒▒▒ ░░
↓
5 ┌─────────────────────────┘
│
↓
░░
▓▓▓▓▓▓ ▒▒▒▒
↓
4 └───────────────────────────────────────────────────┐
│
↓
░░
▒▒▒▒ ▓▓▓▓▓▓
↓
3 ┌─────────────────────────┘
│
↓
░░ ▒▒▒▒ ▓▓▓▓▓▓
↓
2 └─────────────────────────┐
│
↓
▒▒▒▒
░░ ▓▓▓▓▓▓
↓
1 └───────────────────────────────────────────────────┐
│
↓
░░
▒▒▒▒
▓▓▓▓▓▓
The minimum number of moves to solve a 3-disk Tower of Hanoi is 7
</pre>
=={{header|Ring}}==
<syntaxhighlight lang="ring">
move(4, 1, 2, 3)
func move n, src, dst, via
if n > 0 move(n - 1, src, via, dst)
see "" + src + " to " + dst + nl
move(n - 1, via, dst, src) ok
</syntaxhighlight>
=={{header|RPL}}==
{{trans|Python}}
{{works with|Halcyon Calc|4.2.7}}
≪ → ndisks start end
≪ '''IF''' ndisks '''THEN'''
ndisks 1 - start 6 start - end - '''HANOI'''
start →STR " → " + end →STR +
ndisks 1 - 6 start - end - end '''HANOI'''
'''END'''
≫ ≫ ''''HANOI'''' STO
3 1 3 '''HANOI'''
{{out}}
<pre>
7: "1 → 3"
6: "1 → 2"
5: "3 → 2"
4: "1 → 3"
3: "2 → 1"
2: "2 → 3"
1: "1 → 3"
</pre>
=={{header|Ruby}}==
===version 1===
<syntaxhighlight lang="ruby">def move(num_disks, start=0, target=1, using=2)
if num_disks == 1
@towers[target] << @towers[start].pop
puts "Move disk from #{start} to #{target} : #{@towers}"
else
move(num_disks-1, start, using, target)
move(1, start, target, using)
move(num_disks-1, using, target, start)
end
end
n = 5
@towers = [[*1..n].reverse, [], []]
move(n)</syntaxhighlight>
{{out}}
<pre>
Move disk from 0 to 1 : [[5, 4, 3, 2], [1], []]
Move disk from 0 to 2 : [[5, 4, 3], [1], [2]]
Move disk from 1 to 2 : [[5, 4, 3], [], [2, 1]]
Move disk from 0 to 1 : [[5, 4], [3], [2, 1]]
Move disk from 2 to 0 : [[5, 4, 1], [3], [2]]
Move disk from 2 to 1 : [[5, 4, 1], [3, 2], []]
Move disk from 0 to 1 : [[5, 4], [3, 2, 1], []]
Move disk from 0 to 2 : [[5], [3, 2, 1], [4]]
Move disk from 1 to 2 : [[5], [3, 2], [4, 1]]
Move disk from 1 to 0 : [[5, 2], [3], [4, 1]]
Move disk from 2 to 0 : [[5, 2, 1], [3], [4]]
Move disk from 1 to 2 : [[5, 2, 1], [], [4, 3]]
Move disk from 0 to 1 : [[5, 2], [1], [4, 3]]
Move disk from 0 to 2 : [[5], [1], [4, 3, 2]]
Move disk from 1 to 2 : [[5], [], [4, 3, 2, 1]]
Move disk from 0 to 1 : [[], [5], [4, 3, 2, 1]]
Move disk from 2 to 0 : [[1], [5], [4, 3, 2]]
Move disk from 2 to 1 : [[1], [5, 2], [4, 3]]
Move disk from 0 to 1 : [[], [5, 2, 1], [4, 3]]
Move disk from 2 to 0 : [[3], [5, 2, 1], [4]]
Move disk from 1 to 2 : [[3], [5, 2], [4, 1]]
Move disk from 1 to 0 : [[3, 2], [5], [4, 1]]
Move disk from 2 to 0 : [[3, 2, 1], [5], [4]]
Move disk from 2 to 1 : [[3, 2, 1], [5, 4], []]
Move disk from 0 to 1 : [[3, 2], [5, 4, 1], []]
Move disk from 0 to 2 : [[3], [5, 4, 1], [2]]
Move disk from 1 to 2 : [[3], [5, 4], [2, 1]]
Move disk from 0 to 1 : [[], [5, 4, 3], [2, 1]]
Move disk from 2 to 0 : [[1], [5, 4, 3], [2]]
Move disk from 2 to 1 : [[1], [5, 4, 3, 2], []]
Move disk from 0 to 1 : [[], [5, 4, 3, 2, 1], []]
</pre>
===version 2===
<syntaxhighlight lang="ruby"># solve(source, via, target)
# Example:
# solve([5, 4, 3, 2, 1], [], [])
# Note this will also solve randomly placed disks,
# "place all disk in target with legal moves only".
def solve(*towers)
# total number of disks
disks = towers.inject(0){|sum, tower| sum+tower.length}
x=0 # sequence number
p towers # initial trace
# have we solved the puzzle yet?
while towers.last.length < disks do
x+=1 # assume the next step
from = (x&x-1)%3
to = ((x|(x-1))+1)%3
# can we actually take from tower?
if top = towers[from].last
bottom = towers[to].last
# is the move legal?
if !bottom || bottom > top
# ok, do it!
towers[to].push(towers[from].pop)
p towers # trace
end
end
end
end
solve([5, 4, 3, 2, 1], [], [])</syntaxhighlight>
{{out}}
<pre>
[[5, 4, 3, 2, 1], [], []]
[[5, 4, 3, 2], [], [1]]
[[5, 4, 3], [2], [1]]
[[5, 4, 3], [2, 1], []]
[[5, 4], [2, 1], [3]]
[[5, 4, 1], [2], [3]]
[[5, 4, 1], [], [3, 2]]
[[5, 4], [], [3, 2, 1]]
[[5], [4], [3, 2, 1]]
[[5], [4, 1], [3, 2]]
[[5, 2], [4, 1], [3]]
[[5, 2, 1], [4], [3]]
[[5, 2, 1], [4, 3], []]
[[5, 2], [4, 3], [1]]
[[5], [4, 3, 2], [1]]
[[5], [4, 3, 2, 1], []]
[[], [4, 3, 2, 1], [5]]
[[1], [4, 3, 2], [5]]
[[1], [4, 3], [5, 2]]
[[], [4, 3], [5, 2, 1]]
[[3], [4], [5, 2, 1]]
[[3], [4, 1], [5, 2]]
[[3, 2], [4, 1], [5]]
[[3, 2, 1], [4], [5]]
[[3, 2, 1], [], [5, 4]]
[[3, 2], [], [5, 4, 1]]
[[3], [2], [5, 4, 1]]
[[3], [2, 1], [5, 4]]
[[], [2, 1], [5, 4, 3]]
[[1], [2], [5, 4, 3]]
[[1], [], [5, 4, 3, 2]]
[[], [], [5, 4, 3, 2, 1]]
</pre>
=={{header|Run BASIC}}==
<syntaxhighlight lang="runbasic">a = move(4, "1", "2", "3")
function move(n, a$, b$, c$)
if n > 0 then
a = move(n-1, a$, c$, b$)
print "Move disk from " ; a$ ; " to " ; c$
a = move(n-1, b$, a$, c$)
end if
end function</syntaxhighlight>
<pre>Move disk from 1 to 3
Move disk from 1 to 2
Move disk from 3 to 2
Move disk from 1 to 3
Move disk from 2 to 1
Move disk from 2 to 3
Move disk from 1 to 3
Move disk from 1 to 2
Move disk from 3 to 2
Move disk from 3 to 1
Move disk from 2 to 1
Move disk from 3 to 2
Move disk from 1 to 3
Move disk from 1 to 2
Move disk from 3 to 2</pre>
=={{header|Rust}}==
{{trans|C}}
<syntaxhighlight lang="rust">fn move_(n: i32, from: i32, to: i32, via: i32) {
if n > 0 {
move_(n - 1, from, via, to);
println!("Move disk from pole {} to pole {}", from, to);
move_(n - 1, via, to, from);
}
}
fn main() {
move_(4, 1,2,3);
}</syntaxhighlight>
=={{header|SASL}}==
Copied from SAL manual, Appendix II, answer (3)
<syntaxhighlight lang="sasl">hanoi 8 ‘abc"
WHERE
hanoi 0 (a,b,c,) = ()
hanoi n ( a,b,c) = hanoi (n-1) (a,c,b) ,
‘move a disc from " , a , ‘ to " , b , NL ,
hanoi (n-1) (c,b,a)
?</syntaxhighlight>
=={{header|Sather}}==
{{trans|Fortran}}
<syntaxhighlight lang="sather">class MAIN is
move(ndisks, from, to, via:INT) is
if ndisks = 1 then
#OUT + "Move disk from pole " + from + " to pole " + to + "\n";
else
move(ndisks-1, from, via, to);
move(1, from, to, via);
move(ndisks-1, via, to, from);
end;
end;
main is
move(4, 1, 2, 3);
end;
end;</syntaxhighlight>
=={{header|Scala}}==
<syntaxhighlight lang="scala">def move(n: Int, from: Int, to: Int, via: Int) : Unit = {
if (n == 1) {
Console.println("Move disk from pole " + from + " to pole " + to)
} else {
move(n - 1, from, via, to)
move(1, from, to, via)
move(n - 1, via, to, from)
}
}</syntaxhighlight>
This next example is from http://gist.github.com/66925 it is a translation to Scala of a Prolog solution and solves the problem at compile time
<syntaxhighlight lang="scala">object TowersOfHanoi {
import scala.reflect.Manifest
def simpleName(m:Manifest[_]):String = {
val name = m.toString
name.substring(name.lastIndexOf('$')+1)
}
trait Nat
final class _0 extends Nat
final class Succ[Pre<:Nat] extends Nat
type _1 = Succ[_0]
type _2 = Succ[_1]
type _3 = Succ[_2]
type _4 = Succ[_3]
case class Move[N<:Nat,A,B,C]()
implicit def move0[A,B,C](implicit a:Manifest[A],b:Manifest[B]):Move[_0,A,B,C] = {
System.out.println("Move from "+simpleName(a)+" to "+simpleName(b));null
}
implicit def moveN[P<:Nat,A,B,C](implicit m1:Move[P,A,C,B],m2:Move[_0,A,B,C],m3:Move[P,C,B,A])
:Move[Succ[P],A,B,C] = null
def run[N<:Nat,A,B,C](implicit m:Move[N,A,B,C]) = null
case class Left()
case class Center()
case class Right()
def main(args:Array[String]){
run[_2,Left,Right,Center]
}
}</syntaxhighlight>
=={{header|Scheme}}==
Recursive Process
<syntaxhighlight lang="scheme">(define (towers-of-hanoi n from to spare)
(define (print-move from to)
(display "Move[")
(display from)
(display ", ")
(display to)
(display "]")
(newline))
(cond ((= n 0) "done")
(else
(towers-of-hanoi (- n 1) from spare to)
(print-move from to)
(towers-of-hanoi (- n 1) spare to from))))
(towers-of-hanoi 3 "A" "B" "C")</syntaxhighlight>
{{out}}
<pre>Move[A, B]
Move[A, C]
Move[B, C]
Move[A, B]
Move[C, A]
Move[C, B]
Move[A, B]
"done"</pre>
=={{header|Seed7}}==
<syntaxhighlight lang="seed7">const proc: hanoi (in integer: disk, in string: source, in string: dest, in string: via) is func
begin
if disk > 0 then
hanoi(pred(disk), source, via, dest);
writeln("Move disk " <& disk <& " from " <& source <& " to " <& dest);
hanoi(pred(disk), via, dest, source);
end if;
end func;</syntaxhighlight>
=={{header|SETL}}==
<syntaxhighlight lang="setl">program hanoi;
loop for [src, dest] in move(4, 1, 2, 3) do
print("Move disk from pole " + src + " to pole " + dest);
end loop;
proc move(n, src, via, dest);
if n=0 then return []; end if;
return move(n-1, src, dest, via)
+ [[src, dest]]
+ move(n-1, via, src, dest);
end proc;
end program;</syntaxhighlight>
{{out}}
<pre>Move disk from pole 1 to pole 2
Move disk from pole 1 to pole 3
Move disk from pole 2 to pole 3
Move disk from pole 1 to pole 2
Move disk from pole 3 to pole 1
Move disk from pole 3 to pole 2
Move disk from pole 1 to pole 2
Move disk from pole 1 to pole 3
Move disk from pole 2 to pole 3
Move disk from pole 2 to pole 1
Move disk from pole 3 to pole 1
Move disk from pole 2 to pole 3
Move disk from pole 1 to pole 2
Move disk from pole 1 to pole 3
Move disk from pole 2 to pole 3</pre>
=={{header|Sidef}}==
{{trans|Perl}}
<syntaxhighlight lang="ruby">func hanoi(n, from=1, to=2, via=3) {
if (n == 1) {
say "Move disk from pole #{from} to pole #{to}.";
} else {
hanoi(n-1, from, via, to);
hanoi( 1, from, to, via);
hanoi(n-1, via, to, from);
}
}
hanoi(4);</syntaxhighlight>
=={{header|SNOBOL4}}==
<syntaxhighlight lang="snobol4">* # Note: count is global
define('hanoi(n,src,trg,tmp)') :(hanoi_end)
hanoi hanoi = eq(n,0) 1 :s(return)
hanoi(n - 1, src, tmp, trg)
count = count + 1
output = count ': Move disc from ' src ' to ' trg
hanoi(n - 1, tmp, trg, src) :(return)
hanoi_end
* # Test with 4 discs
hanoi(4,'A','C','B')
end</syntaxhighlight>
{{out}}
<pre>1: Move disc from A to B
2: Move disc from A to C
3: Move disc from B to C
4: Move disc from A to B
5: Move disc from C to A
6: Move disc from C to B
7: Move disc from A to B
8: Move disc from A to C
9: Move disc from B to C
10: Move disc from B to A
11: Move disc from C to A
12: Move disc from B to C
13: Move disc from A to B
14: Move disc from A to C
15: Move disc from B to C</pre>
=={{header|SparForte}}==
As a structured script.
<syntaxhighlight lang="ada">#!/usr/local/bin/spar
pragma annotate( summary, "hanoi" )
@( description, "Solve the Towers of Hanoi problem with recursion." )
@( see_also, "https://rosettacode.org/wiki/Towers_of_Hanoi" )
@( author, "Ken O. Burtch" );
pragma license( unrestricted );
pragma restriction( no_external_commands );
procedure hanoi is
type pegs is (left, center, right);
-- Determine the moves
procedure solve( num_disks : natural; start_peg : pegs; end_peg : pegs; via_peg : pegs ) is
begin
if num_disks > 0 then
solve( num_disks - 1, start_peg, via_peg, end_peg );
put( "Move disk" )@( num_disks )@( " from " )@( start_peg )@( " to " )@( end_peg );
new_line;
solve( num_disks - 1, via_peg, end_peg, start_peg );
end if;
end solve;
begin
-- solve with 4 disks at the left
--solve( 4, left, right, center );
solve( 4, left, right, center );
put_line( "Towers of Hanoi puzzle completed" );
end hanoi;</syntaxhighlight>
=={{header|Standard ML}}==
fun hanoi(0, a, b, c) = [] |
hanoi(n, a, b, c) = hanoi(n-1, a, c, b) @ [(a,b)] @ hanoi(n-1, c, b, a);
=={{header|Stata}}==
<syntaxhighlight lang="stata">function hanoi(n, a, b, c) {
if (n>0) {
hanoi(n-1, a, c, b)
printf("Move from %f to %f\n", a, b)
hanoi(n-1, c, b, a)
}
}
hanoi(3, 1, 2, 3)
Move from 1 to 2
Move from 1 to 3
Move from 2 to 3
Move from 1 to 2
Move from 3 to 1
Move from 3 to 2
Move from 1 to 2</syntaxhighlight>
=={{header|Swift}}==
{{trans|JavaScript}}
<syntaxhighlight lang="swift">func hanoi(n:Int, a:String, b:String, c:String) {
if (n > 0) {
hanoi(n - 1, a, c, b)
println("Move disk from \(a) to \(c)")
hanoi(n - 1, b, a, c)
}
}
hanoi(4, "A", "B", "C")</syntaxhighlight>
'''Swift 2.1'''
<syntaxhighlight lang="swift">func hanoi(n:Int, a:String, b:String, c:String) {
if (n > 0) {
hanoi(n - 1, a: a, b: c, c: b)
print("Move disk from \(a) to \(c)")
hanoi(n - 1, a: b, b: a, c: c)
}
}
hanoi(4, a:"A", b:"B", c:"C")</syntaxhighlight>
=={{header|Tcl}}==
The use of <code>interp alias</code> shown is a sort of closure: keep track of the number of moves required
<syntaxhighlight lang="tcl">interp alias {} hanoi {} do_hanoi 0
proc do_hanoi {count n {from A} {to C} {via B}} {
if {$n == 1} {
interp alias {} hanoi {} do_hanoi [incr count]
puts "$count: move from $from to $to"
} else {
incr n -1
hanoi $n $from $via $to
hanoi 1 $from $to $via
hanoi $n $via $to $from
}
}
hanoi 4</syntaxhighlight>
{{out}}
<pre>1: move from A to B
2: move from A to C
3: move from B to C
4: move from A to B
5: move from C to A
6: move from C to B
7: move from A to B
8: move from A to C
9: move from B to C
10: move from B to A
11: move from C to A
12: move from B to C
13: move from A to B
14: move from A to C
15: move from B to C</pre>
=={{header|TI-83 BASIC}}==
TI-83 BASIC lacks recursion, so technically this task is impossible, however here is a version that uses an iterative method.
<syntaxhighlight lang="ti-83b">PROGRAM:TOHSOLVE
0→A
1→B
0→C
0→D
0→M
1→R
While A<1 or A>7
Input "No. of rings=?",A
End
randM(A+1,3)→[C]
[[1,2][1,3][2,3]]→[E]
Fill(0,[C])
For(I,1,A,1)
I?[C](I,1)
End
ClrHome
While [C](1,3)≠1 and [C](1,2)≠1
For(J,1,3)
For(I,1,A)
If [C](I,J)≠0:Then
Output(I+1,3J,[C](I,J))
End
End
End
While C=0
Output(1,3B," ")
1→I
[E](R,2)→J
While [C](I,J)=0 and I≤A
I+1→I
End
[C](I,J)→D
1→I
[E](R,1)→J
While [C](I,J)=0 and I≤A
I+1→I
End
If (D<[C](I,J) and D≠0) or [C](I,J)=0:Then
[E](R,2)→B
Else
[E](R,1)→B
End
1→I
While [C](I,B)=0 and I≤A
I+1→I
End
If I≤A:Then
[C](I,B)→C
0→[C](I,B)
Output(I+1,3B," ")
End
Output(1,3B,"V")
End
While C≠0
Output(1,3B," ")
If B=[E](R,2):Then
[E](R,1)→B
Else
[E](R,2)→B
End
1→I
While [C](I,B)=0 and I≤A
I+1→I
End
If [C](I,B)=0 or [C](I,B)>C:Then
C→[C](I-1,B)
0→C
M+1→M
End
End
Output(1,3B,"V")
R+1→R
If R=4:Then:1→R:End
End
</syntaxhighlight>
=={{header|Tiny BASIC}}==
Tiny BASIC does not have recursion, so only an iterative solution is possible... and it has no arrays, so actually keeping track of individual discs is not feasible.
But as if by magic, it turns out that the source and destination pegs on iteration number n are given by (n&n-1) mod 3 and ((n|n-1) + 1) mod 3 respectively, where & and | are the bitwise and and or operators. Line 40 onward is dedicated to implementing those bitwise operations, since Tiny BASIC hasn't got them natively.
<syntaxhighlight lang="tinybasic"> 5 PRINT "How many disks?"
INPUT D
IF D < 1 THEN GOTO 5
IF D > 10 THEN GOTO 5
LET N = 1
10 IF D = 0 THEN GOTO 20
LET D = D - 1
LET N = 2*N
GOTO 10
20 LET X = 0
30 LET X = X + 1
IF X = N THEN END
GOSUB 40
LET S = S - 3*(S/3)
GOSUB 50
LET T = T + 1
LET T = T - 3*(T/3)
PRINT "Move disc on peg ",S+1," to peg ",T+1
GOTO 30
40 LET B = X - 1
LET A = X
LET S = 0
LET Z = 2048
45 LET C = 0
IF B >= Z THEN LET C = 1
IF A >= Z THEN LET C = C + 1
IF C = 2 THEN LET S = S + Z
IF A >= Z THEN LET A = A - Z
IF B >= Z THEN LET B = B - Z
LET Z = Z / 2
IF Z = 0 THEN RETURN
GOTO 45
50 LET B = X - 1
LET A = X
LET T = 0
LET Z = 2048
55 LET C = 0
IF B >= Z THEN LET C = 1
IF A >= Z THEN LET C = C + 1
IF C > 0 THEN LET T = T + Z
IF A >= Z THEN LET A = A - Z
IF B >= Z THEN LET B = B - Z
LET Z = Z / 2
IF Z = 0 THEN RETURN
GOTO 55</syntaxhighlight>
{{out}}<pre>
How many discs?
4
Move disc on peg 1 to peg 3
Move disc on peg 1 to peg 2
Move disc on peg 3 to peg 2
Move disc on peg 1 to peg 3
Move disc on peg 2 to peg 1
Move disc on peg 2 to peg 3
Move disc on peg 1 to peg 3
Move disc on peg 1 to peg 2
Move disc on peg 3 to peg 2
Move disc on peg 3 to peg 1
Move disc on peg 2 to peg 1
Move disc on peg 3 to peg 2
Move disc on peg 1 to peg 3
Move disc on peg 1 to peg 2
Move disc on peg 3 to peg 2
</pre>
=={{header|Toka}}==
<syntaxhighlight lang="toka">value| sa sb sc n |
[ to sc to sb to sa to n ] is vars!
[ ( num from to via -- )
vars!
n 0 <>
[
n sa sb sc
n 1- sa sc sb recurse
vars!
." Move a ring from " sa . ." to " sb . cr
n 1- sc sb sa recurse
] ifTrue
] is hanoi</syntaxhighlight>
=={{header|True BASIC}}==
{{trans|FreeBASIC}}
<syntaxhighlight lang="basic">
DECLARE SUB hanoi
SUB hanoi(n, desde , hasta, via)
IF n > 0 THEN
CALL hanoi(n - 1, desde, via, hasta)
PRINT "Mover disco"; n; "desde posición"; desde; "hasta posición"; hasta
CALL hanoi(n - 1, via, hasta, desde)
END IF
END SUB
PRINT "Tres discos"
PRINT
CALL hanoi(3, 1, 2, 3)
PRINT
PRINT "Cuatro discos"
PRINT
CALL hanoi(4, 1, 2, 3)
PRINT
PRINT "Pulsa un tecla para salir"
END
</syntaxhighlight>
=={{header|TSE SAL}}==
<syntaxhighlight lang="tsesal">// library: program: run: towersofhanoi: recursive: sub <description></description> <version>1.0.0.0.0</version> <version control></version control> (filenamemacro=runprrsu.s) [kn, ri, tu, 07-02-2012 19:54:23]
PROC PROCProgramRunTowersofhanoiRecursiveSub( INTEGER totalDiskI, STRING fromS, STRING toS, STRING viaS, INTEGER bufferI )
IF ( totalDiskI == 0 )
RETURN()
ENDIF
PROCProgramRunTowersofhanoiRecursiveSub( totalDiskI - 1, fromS, viaS, toS, bufferI )
AddLine( Format( "Move disk", " ", totalDiskI, " ", "from peg", " ", "'", fromS, "'", " ", "to peg", " ", "'", toS, "'" ), bufferI )
PROCProgramRunTowersofhanoiRecursiveSub( totalDiskI - 1, viaS, toS, fromS, bufferI )
END
// library: program: run: towersofhanoi: recursive <description></description> <version>1.0.0.0.6</version> <version control></version control> (filenamemacro=runprtre.s) [kn, ri, tu, 07-02-2012 19:40:45]
PROC PROCProgramRunTowersofhanoiRecursive( INTEGER totalDiskI, STRING fromS, STRING toS, STRING viaS )
INTEGER bufferI = 0
PushPosition()
bufferI = CreateTempBuffer()
PopPosition()
PROCProgramRunTowersofhanoiRecursiveSub( totalDiskI, fromS, toS, viaS, bufferI )
GotoBufferId( bufferI )
END
PROC Main()
STRING s1[255] = "4"
IF ( NOT ( Ask( "program: run: towersofhanoi: recursive: totalDiskI = ", s1, _EDIT_HISTORY_ ) ) AND ( Length( s1 ) > 0 ) ) RETURN() ENDIF
PROCProgramRunTowersofhanoiRecursive( Val( s1 ), "source", "target", "via" )
END</syntaxhighlight>
=={{header|uBasic/4tH}}==
{{trans|C}}
<syntaxhighlight lang="text">Proc _Move(4, 1,2,3) ' 4 disks, 3 poles
End
_Move Param(4)
If (a@ > 0) Then
Proc _Move (a@ - 1, b@, d@, c@)
Print "Move disk from pole ";b@;" to pole ";c@
Proc _Move (a@ - 1, d@, c@, b@)
EndIf
Return</syntaxhighlight>
=={{header|Uiua}}==
{{works with|Uiua|0.10.0}}
<syntaxhighlight lang="bash">
F ← |1.0 (
⟨
&p ⊏[1 2] &pf "Move disc [from to]: "
| F⍜(⊡0|-1)⍜(⊏[2 3]|⇌).
F⍜(⊡0|1◌).
F⍜(⊡0|-1)⍜(⊏[1 3]|⇌)
⟩≠1⊢.
)
F [4 1 2 3]
</syntaxhighlight>
{{out}}
<pre>
Move disc [from to]: [1 3]
Move disc [from to]: [1 2]
Move disc [from to]: [3 2]
Move disc [from to]: [1 3]
Move disc [from to]: [2 1]
Move disc [from to]: [2 3]
Move disc [from to]: [1 3]
Move disc [from to]: [1 2]
Move disc [from to]: [3 2]
Move disc [from to]: [3 1]
Move disc [from to]: [2 1]
Move disc [from to]: [3 2]
Move disc [from to]: [1 3]
Move disc [from to]: [1 2]
Move disc [from to]: [3 2]
</pre>
=={{header|UNIX Shell}}==
{{works with|Bourne Again SHell}}
{{works with|Korn Shell}}
{{works with|Z Shell}}
<syntaxhighlight lang="bash">function move {
typeset -i n=$1
typeset from=$2
typeset to=$3
typeset via=$4
if (( n )); then
move $(( n - 1 )) "$from" "$via" "$to"
echo "Move disk from pole $from to pole $to"
move $(( n - 1 )) "$via" "$to" "$from"
fi
}
move "$@"</syntaxhighlight>
A strict POSIX (or just really old) shell has no subprogram capability, but scripts are naturally reentrant, so:
{{works with|Bourne Shell}}
{{works with|Almquist Shell}}
<syntaxhighlight lang="bash">#!/bin/sh
if [ "$1" -gt 0 ]; then
"$0" "`expr $1 - 1`" "$2" "$4" "$3"
echo "Move disk from pole $2 to pole $3"
"$0" "`expr $1 - 1`" "$4" "$3" "$2"
fi
</syntaxhighlight>
Output from any of the above:
{{Out}}
<pre>$ hanoi 4 1 3 2
Move disk from pole 1 to pole 2
Move disk from pole 1 to pole 3
Move disk from pole 2 to pole 3
Move disk from pole 1 to pole 2
Move disk from pole 3 to pole 1
Move disk from pole 3 to pole 2
Move disk from pole 1 to pole 2
Move disk from pole 1 to pole 3
Move disk from pole 2 to pole 3
Move disk from pole 2 to pole 1
Move disk from pole 3 to pole 1
Move disk from pole 2 to pole 3
Move disk from pole 1 to pole 2
Move disk from pole 1 to pole 3
Move disk from pole 2 to pole 3</pre>
=={{header|Ursala}}==
<syntaxhighlight lang="ursala">#import nat
move = ~&al^& ^rlPlrrPCT/~&arhthPX ^|W/~& ^|G/predecessor ^/~&htxPC ~&zyxPC
#show+
main = ^|T(~&,' -> '--)* move/4 <'start','end','middle'></syntaxhighlight>
{{out}}
<pre>start -> middle
start -> end
middle -> end
start -> middle
end -> start
end -> middle
start -> middle
start -> end
middle -> end
middle -> start
end -> start
middle -> end
start -> middle
start -> end
middle -> end</pre>
=={{header|Uxntal}}==
<syntaxhighlight lang="Uxntal">|10 @Console &vector $2 &read $1 &pad $4 &type $1 &write $1 &error $1
|0100 ( -> )
#0102 [ LIT2 03 &count 04 ] hanoi
POP2 POP2 BRK
@hanoi ( from spare to count -: from spare to count )
( moving 0 disks is no-op )
DUP ?{ JMP2r }
( move disks 1..count-1 to the spare peg )
#01 SUB ROT SWP hanoi
( from to spare count-1 )
( print the current move )
;dict/move print-str
INCk #30 ORA .Console/write DEO
STH2
;dict/from print-str
OVR #30 ORA .Console/write DEO
;dict/to print-str
DUP #30 ORA .Console/write DEO
[ LIT2 0a -Console/write ] DEO
STH2r
( move disks 1..count-1 from the spare peg to the goal peg )
STH ROT ROT STHr hanoi
( restore original parameters for convenient recursion )
STH2 SWP STH2r INC
JMP2r
@print-str
&loop
LDAk .Console/write DEO
INC2 LDAk ?&loop
POP2 JMP2r
@dict
&move "Move 20 "disk 2000
&from 20 "from 20 "pole 2000
&to 20 "to 20 "pole 2000</syntaxhighlight>
=={{header|VBScript}}==
Derived from the BASIC256 version.
<syntaxhighlight lang="vbscript">Sub Move(n,fromPeg,toPeg,viaPeg)
If n > 0 Then
Move n-1, fromPeg, viaPeg, toPeg
WScript.StdOut.Write "Move disk from " & fromPeg & " to " & toPeg
WScript.StdOut.WriteBlankLines(1)
Move n-1, viaPeg, toPeg, fromPeg
End If
End Sub
Move 4,1,2,3
WScript.StdOut.Write("Towers of Hanoi puzzle completed!")</syntaxhighlight>
{{out}}
<pre>Move disk from 1 to 3
Move disk from 1 to 2
Move disk from 3 to 2
Move disk from 1 to 3
Move disk from 2 to 1
Move disk from 2 to 3
Move disk from 1 to 3
Move disk from 1 to 2
Move disk from 3 to 2
Move disk from 3 to 1
Move disk from 2 to 1
Move disk from 3 to 2
Move disk from 1 to 3
Move disk from 1 to 2
Move disk from 3 to 2
Towers of Hanoi puzzle completed!</pre>
=={{header|Vedit macro language}}==
This implementation outputs the results in current edit buffer.
<syntaxhighlight lang="vedit">#1=1; #2=2; #3=3; #4=4 // move 4 disks from 1 to 2
Call("MOVE_DISKS")
Return
// Move disks
// #1 = from, #2 = to, #3 = via, #4 = number of disks
//
:MOVE_DISKS:
if (#4 > 0) {
Num_Push(1,4)
#9=#2; #2=#3; #3=#9; #4-- // #1 to #3 via #2
Call("MOVE_DISKS")
Num_Pop(1,4)
Ins_Text("Move a disk from ") // move one disk
Num_Ins(#1, LEFT+NOCR)
Ins_Text(" to ")
Num_Ins(#2, LEFT)
Num_Push(1,4)
#9=#1; #1=#3; #3 = #9; #4-- // #3 to #2 via #1
Call("MOVE_DISKS")
Num_Pop(1,4)
}
Return</syntaxhighlight>
=={{header|Vim Script}}==
<syntaxhighlight lang="vimscript">function TowersOfHanoi(n, from, to, via)
if (a:n > 1)
call TowersOfHanoi(a:n-1, a:from, a:via, a:to)
endif
echom("Move a disc from " . a:from . " to " . a:to)
if (a:n > 1)
call TowersOfHanoi(a:n-1, a:via, a:to, a:from)
endif
endfunction
call TowersOfHanoi(4, 1, 3, 2)</syntaxhighlight>
{{Out}}
<pre>Move a disc from 1 to 2
Move a disc from 1 to 3
Move a disc from 2 to 3
Move a disc from 1 to 2
Move a disc from 3 to 1
Move a disc from 3 to 2
Move a disc from 1 to 2
Move a disc from 1 to 3
Move a disc from 2 to 3
Move a disc from 2 to 1
Move a disc from 3 to 1
Move a disc from 2 to 3
Move a disc from 1 to 2
Move a disc from 1 to 3
Move a disc from 2 to 3</pre>
=={{header|Visual Basic .NET}}==
<syntaxhighlight lang="vbnet">Module TowersOfHanoi
Sub MoveTowerDisks(ByVal disks As Integer, ByVal fromTower As Integer, ByVal toTower As Integer, ByVal viaTower As Integer)
If disks > 0 Then
MoveTowerDisks(disks - 1, fromTower, viaTower, toTower)
System.Console.WriteLine("Move disk {0} from {1} to {2}", disks, fromTower, toTower)
MoveTowerDisks(disks - 1, viaTower, toTower, fromTower)
End If
End Sub
Sub Main()
MoveTowerDisks(4, 1, 2, 3)
End Sub
End Module</syntaxhighlight>
=={{header|V (Vlang)}}==
<syntaxhighlight lang="Zig">
fn main() {
hanoi(4, "A", "B", "C")
}
fn hanoi(n u64, a string, b string, c string) {
if n > 0 {
hanoi(n - 1, a, c, b)
println("Move disk from ${a} to ${c}")
hanoi(n - 1, b, a, c)
}
}
</syntaxhighlight>
{{out}}
<pre>
Move disk from A to B
Move disk from A to C
Move disk from B to C
Move disk from A to B
Move disk from C to A
Move disk from C to B
Move disk from A to B
Move disk from A to C
Move disk from B to C
Move disk from B to A
Move disk from C to A
Move disk from B to C
Move disk from A to B
Move disk from A to C
Move disk from B to C
</pre>
=={{header|VTL-2}}==
VTL-2 doesn't have procedure parameters, so this stacks and unstacks the return line number and parameters as reuired. The "move" routune starts at line 2000, the routine at 4000 stacks the return line number and parameters for "move" and the routine at 5000 unstacks the return line number and parameters.
<syntaxhighlight lang="vtl2">1000 N=4
1010 F=1
1020 T=2
1030 V=3
1040 S=0
1050 #=2000
1060 #=9999
2000 R=!
2010 #=N<1*2210
2020 #=4000
2030 N=N-1
2040 A=T
2050 T=V
2060 V=A
2070 #=2000
2080 #=5000
2090 ?="Move disk from peg: ";
2100 ?=F
2110 ?=" to peg: ";
2120 ?=T
2130 ?=""
2140 #=4000
2150 N=N-1
2160 A=F
2170 F=V
2180 V=A
2190 #=2000
2200 #=5000
2210 #=R
4000 S=S+1
4010 :S)=R
4020 S=S+1
4030 :S)=N
4040 S=S+1
4050 :S)=F
4060 S=S+1
4070 :S)=V
4080 S=S+1
4090 :S)=T
4100 #=!
5000 T=:S)
5010 S=S-1
5020 V=:S)
5030 S=S-1
5040 F=:S)
5050 S=S-1
5060 N=:S)
5070 S=S-1
5080 R=:S)
5090 S=S-1
5100 #=!</syntaxhighlight>
{{out}}
<pre>
Move disk from peg: 1 to peg: 3
Move disk from peg: 1 to peg: 2
Move disk from peg: 3 to peg: 2
Move disk from peg: 1 to peg: 3
Move disk from peg: 2 to peg: 1
Move disk from peg: 2 to peg: 3
Move disk from peg: 1 to peg: 3
Move disk from peg: 1 to peg: 2
Move disk from peg: 3 to peg: 2
Move disk from peg: 3 to peg: 1
Move disk from peg: 2 to peg: 1
Move disk from peg: 3 to peg: 2
Move disk from peg: 1 to peg: 3
Move disk from peg: 1 to peg: 2
Move disk from peg: 3 to peg: 2
</pre>
=={{header|Wren}}==
{{trans|Kotlin}}
<syntaxhighlight lang="wren">class Hanoi {
construct new(disks) {
_moves = 0
System.print("Towers of Hanoi with %(disks) disks:\n")
move(disks, "L", "C", "R")
System.print("\nCompleted in %(_moves) moves\n")
}
move(n, from, to, via) {
if (n > 0) {
move(n - 1, from, via, to)
_moves = _moves + 1
System.print("Move disk %(n) from %(from) to %(to)")
move(n - 1, via, to, from)
}
}
}
Hanoi.new(3)
Hanoi.new(4)</syntaxhighlight>
{{out}}
<pre>
Towers of Hanoi with 3 disks:
Move disk 1 from L to C
Move disk 2 from L to R
Move disk 1 from C to R
Move disk 3 from L to C
Move disk 1 from R to L
Move disk 2 from R to C
Move disk 1 from L to C
Completed in 7 moves
Towers of Hanoi with 4 disks:
Move disk 1 from L to R
Move disk 2 from L to C
Move disk 1 from R to C
Move disk 3 from L to R
Move disk 1 from C to L
Move disk 2 from C to R
Move disk 1 from L to R
Move disk 4 from L to C
Move disk 1 from R to C
Move disk 2 from R to L
Move disk 1 from C to L
Move disk 3 from R to C
Move disk 1 from L to R
Move disk 2 from L to C
Move disk 1 from R to C
Completed in 15 moves
</pre>
=={{header|XBasic}}==
{{works with|Windows XBasic}}
<syntaxhighlight lang="qbasic">PROGRAM "Hanoi"
VERSION "0.0000"
DECLARE FUNCTION Entry ()
DECLARE FUNCTION Hanoi(n, desde , hasta, via)
FUNCTION Entry ()
PRINT "Three disks\n"
Hanoi (3, 1, 2, 3)
PRINT "\nFour discks\n"
Hanoi (4, 1, 2, 3)
PRINT "\nTowers of Hanoi puzzle completed!"
END FUNCTION
FUNCTION Hanoi (n, desde , hasta, via)
IF n > 0 THEN
Hanoi (n - 1, desde, via, hasta)
PRINT "Move disk"; n; " from pole"; desde; " to pole"; hasta
Hanoi (n - 1, via, hasta, desde)
END IF
END FUNCTION
END PROGRAM</syntaxhighlight>
{{out}}
<pre>Same as FreeBASIC entry.</pre>
=={{header|XPL0}}==
<syntaxhighlight lang="xpl0">code Text=12;
proc MoveTower(Discs, From, To, Using);
int Discs, From, To, Using;
[if Discs > 0 then
[MoveTower(Discs-1, From, Using, To);
Text(0, "Move from "); Text(0, From);
Text(0, " peg to "); Text(0, To); Text(0, " peg.^M^J");
MoveTower(Discs-1, Using, To, From);
];
];
MoveTower(3, "left", "right", "center")</syntaxhighlight>
{{out}}
<pre>
Move from left peg to right peg.
Move from left peg to center peg.
Move from right peg to center peg.
Move from left peg to right peg.
Move from center peg to left peg.
Move from center peg to right peg.
Move from left peg to right peg.
</pre>
=={{header|XQuery}}==
<syntaxhighlight lang="xquery">declare function local:hanoi($disk as xs:integer, $from as xs:integer,
$to as xs:integer, $via as xs:integer) as element()*
{
if($disk > 0)
then (
local:hanoi($disk - 1, $from, $via, $to),
<move disk='{$disk}'><from>{$from}</from><to>{$to}</to></move>,
local:hanoi($disk - 1, $via, $to, $from)
)
else ()
};
<hanoi>
{
local:hanoi(4, 1, 2, 3)
}
</hanoi></syntaxhighlight>
{{out}}
<syntaxhighlight lang="xml"><?xml version="1.0" encoding="UTF-8"?>
<hanoi>
<move disk="1">
<from>1</from>
<to>3</to>
</move>
<move disk="2">
<from>1</from>
<to>2</to>
</move>
<move disk="1">
<from>3</from>
<to>2</to>
</move>
<move disk="3">
<from>1</from>
<to>3</to>
</move>
<move disk="1">
<from>2</from>
<to>1</to>
</move>
<move disk="2">
<from>2</from>
<to>3</to>
</move>
<move disk="1">
<from>1</from>
<to>3</to>
</move>
<move disk="4">
<from>1</from>
<to>2</to>
</move>
<move disk="1">
<from>3</from>
<to>2</to>
</move>
<move disk="2">
<from>3</from>
<to>1</to>
</move>
<move disk="1">
<from>2</from>
<to>1</to>
</move>
<move disk="3">
<from>3</from>
<to>2</to>
</move>
<move disk="1">
<from>1</from>
<to>3</to>
</move>
<move disk="2">
<from>1</from>
<to>2</to>
</move>
<move disk="1">
<from>3</from>
<to>2</to>
</move>
</hanoi></syntaxhighlight>
=={{header|XSLT}}==
<syntaxhighlight lang="xml"><xsl:template name="hanoi">
<xsl:param name="n"/>
<xsl:param name="from">left</xsl:param>
<xsl:param name="to">middle</xsl:param>
<xsl:param name="via">right</xsl:param>
<xsl:if test="$n > 0">
<xsl:call-template name="hanoi">
<xsl:with-param name="n" select="$n - 1"/>
<xsl:with-param name="from" select="$from"/>
<xsl:with-param name="to" select="$via"/>
<xsl:with-param name="via" select="$to"/>
</xsl:call-template>
<fo:block>
<xsl:text>Move disk from </xsl:text>
<xsl:value-of select="$from"/>
<xsl:text> to </xsl:text>
<xsl:value-of select="$to"/>
</fo:block>
<xsl:call-template name="hanoi">
<xsl:with-param name="n" select="$n - 1"/>
<xsl:with-param name="from" select="$via"/>
<xsl:with-param name="to" select="$to"/>
<xsl:with-param name="via" select="$from"/>
</xsl:call-template>
</xsl:if>
</xsl:template></syntaxhighlight>
<xsl:call-template name="hanoi"><xsl:with-param name="n" select="4"/></xsl:call-template>
=={{header|Yabasic}}==
<syntaxhighlight lang="yabasic">sub hanoi(ndisks, startPeg, endPeg)
if ndisks then
hanoi(ndisks-1, startPeg, 6-startPeg-endPeg)
//print "Move disk ", ndisks, " from ", startPeg, " to ", endPeg
hanoi(ndisks-1, 6-startPeg-endPeg, endPeg)
end if
end sub
print "Be patient, please.\n\n"
print "Hanoi 1 ellapsed ... ";
t1 = peek("millisrunning")
hanoi(22, 1, 3)
t2 = peek("millisrunning")
print t2-t1, " ms"
sub hanoi2(n, from, to_, via)
if n = 1 then
//print "Move from ", from, " to ", to_
else
hanoi2(n - 1, from, via , to_ )
hanoi2(1 , from, to_ , via )
hanoi2(n - 1, via , to_ , from)
end if
end sub
print "Hanoi 2 ellapsed ... ";
hanoi2(22, 1, 3, 2)
print peek("millisrunning") - t2, " ms"</syntaxhighlight>
=={{header|Z80 Assembly}}==
{{works with|CP/M 3.1|YAZE-AG-2.51.2 Z80 emulator}}
{{works with|ZSM4 macro assembler|YAZE-AG-2.51.2 Z80 emulator}}
Use the /S8 switch on the ZSM4 assembler for 8 significant characters for labels and names<br><br>
<syntaxhighlight lang="z80">
;
; Towers of Hanoi using Z80 assembly language
;
; Runs under CP/M 3.1 on YAZE-AG-2.51.2 Z80 emulator
; Assembled with zsm4 on same emulator/OS, uses macro capabilities of said assembler
; Created with vim under Windows
;
; 2023-05-29 Xorph
;
;
; Useful definitions
;
bdos equ 05h ; Call to CP/M BDOS function
strdel equ 6eh ; Set string delimiter
wrtstr equ 09h ; Write string to console
nul equ 00h ; ASCII control characters
cr equ 0dh
lf equ 0ah
cnull equ '0' ; ASCII character constants
ca equ 'A'
cb equ 'B'
cc equ 'C'
disks equ 4 ; Number of disks to move
;
; Macros for BDOS calls
;
setdel macro char ; Set string delimiter to char
ld c,strdel
ld e,char
call bdos
endm
print macro msg ; Output string to console
ld c,wrtstr
ld de,msg
call bdos
endm
pushall macro ; Save required registers to stack
push af
push bc
push de
endm
popall macro ; Recall required registers from stack
pop de
pop bc
pop af
endm
;
; =====================
; Start of main program
; =====================
;
cseg
setdel nul ; Set string delimiter to 00h
ld a,disks ; Initialization:
ld b,ca ; Tower A is source
ld c,cb ; Tower B is target
ld d,cc ; Tower C is intermediate
hanoi:
;
; Parameters in registers:
; Move a disks from b (source) to c (target) via d (intermediate)
;
or a ; If 0 disks to move, return
ret z
dec a ; Move all but lowest disk from source to intermediate via target
pushall ; Save registers
ld e,c ; Exchange c and d (target and intermediate)
ld c,d
ld d,e
call hanoi ; First recursion
popall ; Restore registers
ld hl,source ; Print move of lowest disk from source to target, save registers during BDOS call
ld (hl),b ; Source is still in b
ld hl,target
ld (hl),c ; Target is back in c due to popall
pushall
print movement
popall
ld e,b ; Now move stack from intermediate to target via source
ld b,d ; Source is still in b, target in c and intermediate in d
ld d,e
jr hanoi ; Optimize tail recursion
;
; ================
; Data definitions
; ================
;
dseg
movement:
defb 'Move disk from tower '
source:
defs 1
defb ' to tower '
target:
defs 1
crlf:
defb cr,lf,nul
</syntaxhighlight>
{{out}}
<pre>
E>hanoi
Move disk from tower A to tower C
Move disk from tower A to tower B
Move disk from tower C to tower B
Move disk from tower A to tower C
Move disk from tower B to tower A
Move disk from tower B to tower C
Move disk from tower A to tower C
Move disk from tower A to tower B
Move disk from tower C to tower B
Move disk from tower C to tower A
Move disk from tower B to tower A
Move disk from tower C to tower B
Move disk from tower A to tower C
Move disk from tower A to tower B
Move disk from tower C to tower B
E>
</pre>
=={{header|Zig}}==
{{trans|C}}
<syntaxhighlight lang="zig">const std = @import("std");
pub fn print(from: u32, to: u32) void {
std.log.info("Moving disk from rod {} to rod {}", .{ from, to });
}
pub fn move(n: u32, from: u32, via: u32, to: u32) void {
if (n > 1) {
move(n - 1, from, to, via);
print(from, to);
move(n - 1, via, from, to);
} else {
print(from, to);
}
}
pub fn main() !void {
move(4, 1, 2, 3);
}
</syntaxhighlight>
=={{header|zkl}}==
{{trans|C}}
<syntaxhighlight lang="zkl">fcn move(n, from,to,via){
if (n>0){
move(n-1, from,via,to);
println("Move disk from pole %d to pole %d".fmt(from, to));
move(n-1, via,to,from);
}
}
move(3, 1,2,3);</syntaxhighlight>
{{out}}
<pre>
Move disk from pole 1 to pole 2
Move disk from pole 1 to pole 3
Move disk from pole 2 to pole 3
Move disk from pole 1 to pole 2
Move disk from pole 3 to pole 1
Move disk from pole 3 to pole 2
Move disk from pole 1 to pole 2
</pre>
[[Category:Puzzles]]
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