Towers of Hanoi: Difference between revisions
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{{task|Classic CS problems and programs}}[[Category:Recursion]][[Category:Games]]
In this task, the goal is to solve the [[wp:Towers_of_Hanoi|Towers of Hanoi]] problem with recursion.
=={{header|360 Assembly}}==
{{trans|PLI}}
<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),POLEX+0 from
MVC POLEN+1(1),POLEX+2 via
MVC POLEN+2(1),POLEX+1 to
L R3,POLEN new poles
BAL R14,MOVE call move(n-1,from,via,to)
LA R2,1 n=1
MVC POLEN+0(1),POLEX+0 from
MVC POLEN+1(1),POLEX+1 to
MVC POLEN+2(1),POLEX+2 via
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),POLEX+2 via
MVC POLEN+1(1),POLEX+1 to
MVC POLEN+2(1),POLEX+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
</lang>
{{out}}
<pre style="height:20ex">
1 Move disc from pole 1 to pole 3
2 Move disc from pole 1 to pole 3
3 Move disc from pole 2 to pole 3
4 Move disc from pole 2 to pole 3
5 Move disc from pole 1 to pole 2
6 Move disc from pole 1 to pole 2
7 Move disc from pole 3 to pole 2
8 Move disc from pole 3 to pole 2
9 Move disc from pole 1 to pole 2
10 Move disc from pole 1 to pole 2
11 Move disc from pole 3 to pole 2
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 3
15 Move disc from pole 2 to pole 3
</pre>
=={{header|8th}}==
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