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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
Prototype:
stack<T> st; //declaration
st.empty();
Parameter:
No parameter passed
Return type: Bool (True or False)
- True: Stack is empty
- False: Stack is not empty
Header file to be included:
#include <iostream>
#include <stack>
OR
#include <bits/stdc++.h>
Usage:
The function checks whether a stack is empty or not.
Time complexity: O(1)
Example:
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"
C++ implementation:
#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