recursion

RECURSION USING STACK

package recursion;
import java.util.Stack;
public class Factorial {

	    // Recursive factorial function
    public static int recursiveFactorial(int n) {
        if (n == 0 || n == 1) {
            return 1;
        } else {
            return n * recursiveFactorial(n - 1);
        }
    }

    // Factorial with stack function
    public static int factorialWithStack(int n) {
        // Create a stack to simulate recursion
        Stack<Integer> stack = new Stack<>();
        stack.push(n);  // Push the initial value onto the stack
        int result = 1; // Initialize the result variable to 1

        // Iterate until the stack is empty
        while (!stack.isEmpty()) {
            int num = stack.pop(); // Pop a number from the stack

            // Multiply the result by the popped number
            result *= num;

            // If the popped number is greater than 1, push (num - 1) onto the stack
            if (num > 1) {
                stack.push(num - 1);
            }
        }
        return result; // Return the factorial result
    }

    // Main method to test the recursive and stack-based factorial functions
    public static void main(String[] args) {
        int num = 5; // Number for which factorial is calculated

        // Calculate and print factorial using recursion
        System.out.println("Factorial of " + num + " using recursion: " + recursiveFactorial(num));

        // Calculate and print factorial using stack
        System.out.println("Factorial of " + num + " using stack: " + factorialWithStack(num));
    }
}

TOWER OF HANOI

package recursion;
import java.util.Stack;
public class TowerOfHanoi {
public static void towerOfHanoi(int numDisks, Stack<Integer> source, Stack<Integer> auxiliary, Stack<Integer> destination) {
if (numDisks == 1) {
destination.push(source.pop());
System.out.println("Move disk 1 from source to destination");
return;
}

        towerOfHanoi(numDisks - 1, source, destination, auxiliary);
        destination.push(source.pop());
        System.out.println("Move disk " + numDisks + " from source to destination");
        towerOfHanoi(numDisks - 1, auxiliary, source, destination);
    }

    public static void main(String[] args) {
        int numDisks = 3;
        Stack<Integer> source = new Stack<>();
        Stack<Integer> auxiliary = new Stack<>();
        Stack<Integer> destination = new Stack<>();

        // Initialize source stack with disks
        for (int i = numDisks; i >= 1; i--) {
            source.push(i);
        }

        System.out.println("Initial configuration:");
        System.out.println("Source: " + source);
        System.out.println("Auxiliary: " + auxiliary);
        System.out.println("Destination: " + destination);

        // Solve Tower of Hanoi problem
        towerOfHanoi(numDisks, source, auxiliary, destination);

        System.out.println("Final configuration:");
        System.out.println("Source: " + source);
        System.out.println("Auxiliary: " + auxiliary);
        System.out.println("Destination: " + destination);
    }
}