Question

In the classic problem of the Towers of Hanoi, you have 3 rods and N disks of different sizes which can slide onto any tower. The puzzle starts with disks sorted in ascending order of size from top to bottom (e.g., each disk sits on top of an even larger one).You have the following constraints:

(A) Only one disk can be moved at a time.

(B) A disk is slid off the top of one rod onto the next rod.

(C) A disk can only be placed on top of a larger disk.

Write a java program to move the disks from the first rod to the last using Stacks.

#with comments please

Answer 1

if you have any doubts comment below.

Tower of Hanoi in java using stacks.

import java.util.*;

/* Class TowerOfHanoiUsingStacks */

public class TowerOfHanoiUsingStacks

{

public static int N;

/* Creating Stack array */

public static Stack<Integer>[] tower = new Stack[4];

public static void main(String[] args)

{

Scanner scan = new Scanner(System.in);

tower[1] = new Stack<Integer>();

tower[2] = new Stack<Integer>();

tower[3] = new Stack<Integer>();

/* Accepting number of disks */   

System.out.println("Enter number of disks");

int num = scan.nextInt();

N = num;

toh(num);

}

/* Function to push disks into stack */

public static void toh(int n)

{

for (int d = n; d > 0; d--)

tower[1].push(d);

display();

move(n, 1, 2, 3);   

}

/* Recursive Function to move disks */

public static void move(int n, int a, int b, int c)

{

if (n > 0)

{

move(n-1, a, c, b);   

int d = tower[a].pop();   

tower[c].push(d);

display();   

move(n-1, b, a, c);   

}   

}

/* Function to display */

public static void display()

{

System.out.println(" A | B | C");

System.out.println("---------------");

for(int i = N - 1; i >= 0; i--)

{

String d1 = " ", d2 = " ", d3 = " ";

try

{

d1 = String.valueOf(tower[1].get(i));

}

catch (Exception e){

}

try

{

d2 = String.valueOf(tower[2].get(i));

}

catch(Exception e){

}

try

{

d3 = String.valueOf(tower[3].get(i));

}

catch (Exception e){

}

System.out.println(" "+d1+" | "+d2+" | "+d3);

}

System.out.println("\n");   

}

}