Tutorial

The towers of hanoi is a popular problem. You have three poles and n disks which fit on the poles. All disks have different size. They are stacked on pole 1 in the orders of their size. The largest disk is on the bottom, the smallest is on the top.

The task is to move all disk from pole 1 to pole 3 under the following restrictions.

The recursive algorithm works like the following: move n-1 disk from the starting pole to the pole which is neither start nor target (intermediate), move disk n to the target pole and then move n-1 disk from the intermediate pole to the target pole. The n-1 disks are moved recursively.

Create a Java project "de.vogella.algorithms.towersofhanoi".

Create the following program.

			
package de.vogella.algorithms.towersofhanoi;

/**
 * Towers of Hanoi
 * Pole are labeled 1, 2,3
 * Each disk is also labeled
 * @author Lars Vogel
 *
 */
public class TowersOfHanoi {
	public static void move(int n, int startPole, int endPole) {
		if (n== 0){
			return; 
		}
		int intermediatePole = 6 - startPole - endPole;
		move(n-1, startPole, intermediatePole);
		System.out.println("Move " +n + " from " + startPole + " to " +endPole);
		move(n-1, intermediatePole, endPole);
	}
	
	public static void main(String[] args) {
		move(5, 1, 3);
	}

	
}

		

Please help me to support this article:

Before posting questions, please see the vogella FAQ. If you have questions or find an error in this article please use the www.vogella.de Google Group. I have created a short list how to create good questions which might also help you.