Towers of Hanoi: Difference between revisions
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{{task}}
In this task, the goal is to solve the Towers of Hanoi problem with recursivity.
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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;
==[[AppleScript]]==
[[Category:AppleScript]]
global moves --this is so the handler 'hanoi' can see the 'moves' variable
set moves to ""
hanoi(4, "peg A", "peg C", "peg B")
on hanoi(ndisks, fromPeg, toPeg, withPeg)
if ndisks is greater than 0 then
hanoi(ndisks - 1, fromPeg, withPeg, toPeg)
set moves to moves & "Move disk " & ndisks & " from " & fromPeg & " to " & toPeg & return
hanoi(ndisks - 1, withPeg, toPeg, fromPeg)
end if
return moves
end hanoi
==[[C plus plus|C++]]==
[[Category:C plus plus]]
'''Compiler:''' [[GCC]]
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);
}
}
==[[E]]==
[[Category: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 $toPeg.`)
move(out, n.previous(), viaPeg, toPeg, fromPeg)
}
}
move(stdout, 4, def left {}, def right {}, def middle {})
==[[Forth]]==
[[Category:Forth]]
With locals:
CREATE peg1 ," left "
CREATE peg2 ," middle "
CREATE peg3 ," right "
: .$ 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 ;
Without locals, executable pegs:
: left ." left" ;
: right ." right" ;
: middle ." middle" ;
: print ( t f -- )
CR ." Move disk from " execute ." to " execute ;
: move-disk ( v t f n -- v t f )
dup 1 = if drop 2dup print exit then
1- >R
rot swap R@ ( t v f n-1 ) recurse
rot swap 2dup print
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 ;
==[[Java]]==
[[Category: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);
}
}
==[[Perl]]==
[[Category:Perl]]
sub move {
my $n = shift;
my $from = shift;
my $to = shift;
my $via = shift;
if ($n == 1) {
print "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);
};
};
==[[Pop11]]==
[[Category:Pop11]]
define hanoi(n, src, dst, via);
if n > 0 then
hanoi(n - 1, src, via, dst);
printf('Move disk ' >< n >< ' from ' >< src >< ' to ' >< dst >< '.\n');
hanoi(n - 1, via, dst, src);
endif;
enddefine;
hanoi(4, "left", "middle", "right");
==[[Python]]==
[[Category:Python]]
<pre>
def hanoi(ndisks, startPeg=1, endPeg=3):
if ndisks:
hanoi(ndisks-1, startPeg, 6-startPeg-endPeg)
print "Move disk %d from peg %d to peg %d" % (ndisks, startPeg, endPeg)
hanoi(ndisks-1, 6-startPeg-endPeg, endPeg)
hanoi(ndisks=4)
</pre>
==[[Seed7]]==
[[Category: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;
==[[Toka]]==
[[Category: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
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