// File:  TowersOfHanoi.java

// Recursive solution to the "Towers of Hanoi" problem for any number of disks

import javax.swing.JOptionPane ;

class DiskMover
{
	private int height ;			// number of disks to be moved

	public DiskMover (int height)
	{
		this.height = height ;
	}

    public void moveDisks(char fromPeg, char toPeg, char usingPeg)
    {
  		// recursive method for determining moves

		// MOVES height DISKS FROM fromPeg TO toPeg, USING usingPeg AS AN
		// AUXILLIARY OR "HELPER" PEG
  	
  		if (height == 1)				// trivial case
	       
	       System.out.println("Move a disk from " + fromPeg + " to " + toPeg ) ;
 		
 		else 
 		{
		   // create new DiskMover object with height of current height - 1
		   
		   DiskMover start = new DiskMover(height-1) ;			

		   //  do a height-1 move from starting peg to the auxilliary peg
		   
		   start.moveDisks(fromPeg, usingPeg, toPeg) ;
    
		   //  move last disk to destination peg from starting peg

	       System.out.println("Move a disk from " + fromPeg + " to " + toPeg ) ;
	
		   //  do a height-1 move to destination peg from the auxilliary peg
		
		   start.moveDisks(usingPeg,toPeg,fromPeg) ;
  		}
  	}
}

public class TowersOfHanoi
{
	public static void main (String args[]) 
	{
  		String input = JOptionPane.showInputDialog( "How many disks? " ) ;
		
		int height = Integer.parseInt( input ) ;
		
		System.out.println() ;
  		
  		DiskMover monk = new DiskMover(height) ;
  		
  		monk.moveDisks('A','B','C') ;
		
		System.out.println() ;
  	}
}





















/* sample output

How many disks? 3

Move a disk from A to C
Move a disk from A to B
Move a disk from C to B
Move a disk from A to C
Move a disk from B to A
Move a disk from B to C
Move a disk from A to C


How many disks? 4

Move a disk from A to B
Move a disk from A to C
Move a disk from B to C
Move a disk from A to B
Move a disk from C to A
Move a disk from C to B
Move a disk from A to B
Move a disk from A to C
Move a disk from B to C
Move a disk from B to A
Move a disk from C to A
Move a disk from B to C
Move a disk from A to B
Move a disk from A to C
Move a disk from B to C

*/