# Towers of Hanoi Recursive Ananlysis

March 11, 2013 Leave a comment

Recursive program to towers of hanoi problem

package algorithms.recursion; /** * @author ntallapa * */ public class TowersOfHanoi { /** * This recursive algorithm takes (2^n-1) iterations to complete the task * * @param n number of disks * @param startPole * @param endPole */ public static void move(int n, int startPole, int endPole) { if (n== 0){ return; } // here 6 is summation of poles, i.e, sigma(3) = 3+2+1 = 6 int intermediatePole = 6 - startPole - endPole; // Move nā1 disks from disk 1 to disk 2, using disk 3 as a temporary holding area. move(n-1, startPole, intermediatePole); // Move the last disk (the largest) from disk 1 to disk 3. System.out.println("Move " +n + " from " + startPole + " to " +endPole); // Move nā1 disks from disk 2 to disk 3, using disk 1 as a temporary holding area. move(n-1, intermediatePole, endPole); } public static void main(String[] args) { move(4, 1, 3); } }

For 2 discs we need 3 iterations, 3 discs we need 7 iterations, 4 discs we need 15 iterations, etc… from this it can be realized that to move ‘n’ discs we need (2^n)-1 iterations.

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