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stack::empty() function in C++ STL

C++ STL stack::empty() function with example: In this article, we are going to see how to check whether a stack is empty or not using C++ STL?
Submitted by Radib Kar, on February 03, 2019

C++ STL - stack::empty() function

The function checks whether a stack is empty or not.

Syntax

stack<T> st; //declaration
st.empty();

Parameter(s)

This function does not accept any parameter.

Return value

This function return a boolean value.

• True: Stack is empty
• False: Stack is not empty

Header file

Header file to be included:

#include <iostream>
#include <stack>
OR
#include <bits/stdc++.h>

Sample Input and Output

For a stack of integer,
stack<int> st;
st.push(4);
st.push(5);
stack content:
5 <-- TOP
4
IF (st.empty())
    Print "Stack is empty"
Else 
    Print "Stack is not empty"
    
Output:
Prints "Stack is not empty"
st.pop()
st.pop()
Stack content:
Empty stack
IF (st.empty())
    Print "Stack is empty"
Else 
    Print "Stack is not empty"
    
Output:
Prints "Stack is empty"

Example

#include <bits/stdc++.h>
using namespace std;

int main() {
  cout << "...use of empty function...\n";
  int count = 0;
  stack<int> st;  // declare the stack
  st.push(4);     // pushed 4
  st.push(5);     // pushed 5
  st.push(6);

  cout << "stack elements are:\n";
  while (!st.empty()) {                             // stack not empty
    cout << "top element is:" << st.top() << endl;  // print top element
    st.pop();
    count++;
  }
  if (st.empty())  // to check for empty stack
    cout << "stack empty\n";
  cout << count << " pop operation performed total to make stack empty\n";

  return 0;
}

Output

...use of empty function...
stack elements are:
top element is:6
top element is:5
top element is:4
stack empty
3 pop operation performed total to make stack empty