Java: Check if the stack is a subset of another stack

Last update on May 09 2025 12:50:15 (UTC/GMT +8 hours)

19. Check if one stack is a subset of another stack.

Write a JavaScript program that implements a stack and checks if the stack is a subset of another 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;
  }

  // Method to get the size of the stack
  public int getSize() {
    return top + 1;
  }

  public static boolean isSubset(Stack A, Stack B) {
    Stack temp = new Stack(A.getSize()); // create a temporary stack for A    
    boolean isSubset = true;

    // check each element in A
    while (!A.isEmpty()) {
      int a = A.pop();
      boolean found = false;

      // search for the corresponding element in B
      while (!B.isEmpty()) {
        int b = B.pop();

        if (a == b) {
          found = true;
          break;
        } else {
          temp.push(b);
        }
      }

      // put back the elements popped from B
      while (!temp.isEmpty()) {
        B.push(temp.pop());
      }

      // if corresponding element is not found, A is not a subset of B
      if (!found) {
        isSubset = false;
        break;
      }
    }

    // put back the elements popped from A
    while (!temp.isEmpty()) {
      A.push(temp.pop());
    }

    return isSubset;
  }

  // Method to display the elements of the stack
  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:");
    System.out.println("\nStack-A");
    Stack A = new Stack(5);
    A.push(1);
    A.push(2);
    A.push(3);
    A.display();
    Stack B = new Stack(5);
    B.push(5);
    B.push(4);
    B.push(3);
    B.push(2);
    B.push(1);
    System.out.println("\nStack-B");
    B.display();
    System.out.println("\nCheck Stack A is subset of Stack B!");
    System.out.println(isSubset(A, B));
    System.out.println("\nCheck Stack B is subset of Stack A!");
    System.out.println(isSubset(B, A));
  }
}

Sample Output:

Initialize a stack:

Stack-A
Stack elements: 3 2 1

Stack-B
Stack elements: 1 2 3 4 5

Check Stack A is subset of Stack B!
true

Check Stack B is subset of Stack A!
false

Flowchart:

For more Practice: Solve these Related Problems:

• Write a Java program to implement a method that checks if all elements of one stack are present in another stack using sets.
• Write a Java program to compare two stacks and determine if one is a subset of the other by iterative search.
• Write a Java program to use Java streams to filter and verify that every element in one stack exists in a second stack.
• Write a Java program to implement subset checking for stacks using recursion and a helper function.

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• Java Stack Exercises Home ↩
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