How to Check if a Stack is Empty in C++?

In C++, we have a stack data structure that follows a LIFO (Last In First Out) rule of operation. In this article, we will learn how to check if a stack is empty in C++.

Example:

Input:
myStack = {1, 2, 3 }

Output:
Stack is not Empty

Checking if a Stack is Empty in C++

To check if a stack is empty in C++, we can use the std::stack::empty() function that returns a boolean value true if the stack is empty and false if the stack is not empty.

C++ Program to Check if a Stack is Empty

The below example demonstrates how we can check if a given stack is empty or not in C++ STL.

C++

// C++ program to illustrate how to check if a stack is
// empty
#include <iostream>
#include <stack>
using namespace std;

int main()
{
    // Creating a stack
    stack<int> mystack;

    // Checking if stack is empty
    if (mystack.empty())
        cout << "Stack is empty\n";
    else
        cout << "Stack is not empty\n";

    // Adding elements to the stack
    mystack.push(10);
    mystack.push(20);
    mystack.push(30);

    // Again Checking if stack is empty
    if (mystack.empty())
        cout << "After Updation Stack is empty\n";
    else
        cout << "After Updation Stack is not empty\n";

    return 0;
}

Output

Stack is empty
After Updation Stack is not empty

Time Complexity: O(1)
Auxiliary Space: O(1)