Java: Reverse the elements of a stack

Last update on December 21 2024 09:43:03 (UTC/GMT +8 hours)

Write a Java program to reverse the elements of a stack.

Sample Solution:

Java Code:

import java.util.Scanner;
public class Stack {
  private int[] arr;
  private int top;

  // Constructor to initialize the stack
  public Stack(int size) {
    arr = new int[size];
    top = -1;
  }

  // Method to push an element onto the stack
  public void push(int num) {
    if (top == arr.length - 1) {
      System.out.println("Stack is full");
    } else {
      top++;
      arr[top] = num;
    }
  }

  // Method to pop an element from the stack
  public int pop() {
    if (top == -1) {
      System.out.println("Stack Underflow");
      return -1;
    } else {
      int poppedElement = arr[top];
      top--;
      return poppedElement;
    }
  }

  // Method to get the top element of the stack
  public int peek() {
    if (top == -1) {
      System.out.println("Stack is empty");
      return -1;
    } else {
      return arr[top];
    }
  }

  // Method to check if the stack is empty
  public boolean isEmpty() {
    return top == -1;
  }

  public void reverse() {
    if (top == -1) {
      System.out.println("Stack is empty");
      return;
    }

    int[] reversedArray = new int[arr.length];
    int index = 0;

    while (!isEmpty()) {
      int temp = pop();
      reversedArray[index++] = temp;
    }

    for (int i = 0; i < index; i++) {
      push(reversedArray[i]);
    }
  }
  public void display() {
    if (top == -1) {
      System.out.println("Stack is empty");
    } else {
      System.out.print("Stack elements: ");
      for (int i = top; i >= 0; i--) {
        System.out.print(arr[i] + " ");
      }
      System.out.println();
    }
  }

  public static void main(String[] args) {
    System.out.println("Initialize a stack:");
    Stack stack = new Stack(10);
    System.out.println("\nInput some elements on the stack:");
    stack.push(1);
    stack.push(3);
    stack.push(2);
    stack.push(0);
    stack.push(7);
    stack.push(5);
    stack.display();
    System.out.println("\nReverse the elements of the said stack:");
    stack.reverse();
    stack.display();
    System.out.println("\nInput two more elements on the stack:");
    stack.push(9);
    stack.push(10);
    stack.display();
    System.out.println("\nReverse the elements of the said stack:");
    stack.reverse();
    stack.display();
  }
}

Sample Output:

Initialize a stack:

Input some elements on the stack:
Stack elements: 5 7 0 2 3 1

Reverse the elements of the said stack:
Stack elements: 1 3 2 0 7 5

Input two more elements on the stack:
Stack elements: 10 9 1 3 2 0 7 5

Reverse the elements of the said stack:
Stack elements: 5 7 0 2 3 1 9 10

Flowchart:

Live Demo:

Java Code Editor:

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