Towers of Hanoi

From Rosetta Code
Revision as of 17:16, 30 January 2007 by 82.181.10.168 (talk) (Added Java section)
Task
Towers of Hanoi
You are encouraged to solve this task according to the task description, using any language you may know.

In this task, the goal is to solve the Towers of Hanoi problem with recursivity.

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


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);
   }
 }

Python

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)