stack emplace() in C++ STL

stack top() in C++ STL

Last Updated : 14 Feb, 2025

In C++, the std::stack::top() is used to find the top element of the std::stack container. It is a member function of std::stack class defined inside the <stack> header file. In this article, we will learn how to find the top element of stack using stack::top() in C++.

Example:

C++

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

int main() {
    stack<int> st;
    st.push(5);
    st.push(11);
  	
  	cout << st.top() << endl;
  
    st.push(9);
  	cout << st.top();
    return 0;
}

Output

11
9

stack::top() Syntax

st.top()

where st is the name of std::stack.

Parameters

This function does not take any parameter.

Return Value

Return the top element of the stack container.
If the stack is empty, its behaviour is undefined.

More Examples of stack::top()

The following examples demonstrates the use of stack::top() function in different scenarios:

Example 1: Finding Top Element of Stack after Pop Operation

C++

// C++ Program to illustrate the use of
// stcak::top()
#include <bits/stdc++.h>
using namespace std;

int main() {
    stack<int> st;
    st.push(5);
    st.push(11);
    st.push(9);
	
  	// Top element before pop
    cout << st.top() << endl;
  
  	// Popping the top element
  	st.pop();
  	cout << st.top();
    return 0;
}

Output

9
11

Example 2: Tyring to Find Top Element of Empty Stack

C++

// C++ Program to illustrate the use of
// stcak::top()
#include <bits/stdc++.h>
using namespace std;

int main() {
  
  	// Empty stack
    stack<int> st;
	
  	// Top element of empty stack
    cout << st.top();
    return 0;
}

Output

Undefined behaviour

stack emplace() in C++ STL

A

AyushSaxena

Improve

Article Tags :

Practice Tags :

Similar Reads

Stack in C++ STL

In C++, stack container follows LIFO (Last In First Out) order of insertion and deletion. It means that most recently inserted element is removed first and the first inserted element will be removed last. This is done by inserting and deleting elements at only one end of the stack which is generally

stack empty() and stack size() in C++ STL

The std::stack::size() and std::stack::empty() in C++ are built-in functions that are used to provide information about the size of the stack. They are the member functions of the std::stack container defined inside <stack> header file.stack::empty()The stack::empty() method is used to check w

stack::push() and stack::pop() in C++ STL

The stack::push() and stack::pop() method in stack container is used to insert and delete the element from the top of stack. They are the member functions of std::stack container defined inside <stack> header file. In this article, we will learn how to use stack::push() and stack::pop() method

stack top() in C++ STL

In C++, the std::stack::top() is used to find the top element of the std::stack container. It is a member function of std::stack class defined inside the <stack> header file. In this article, we will learn how to find the top element of stack using stack::top() in C++.Example:C++#include <b

stack emplace() in C++ STL

Stacks are a type of container adaptors with LIFO(Last In First Out) type of working, where a new element is added at one end (top) and an element is removed from that end only. stack::emplace() This function is used to insert a new element into the stack container, the new element is added on top o

stack swap() in C++ STL

Stacks are a type of container adaptors with LIFO(Last In First Out) type of work, where a new element is added at one end and (top) an element is removed from that end only.stack::swap()This function is used to swap the contents of one stack with another stack of same type but the size may vary. Sy

List of Stacks in C++ STL

Prerequisite: List, Stack Lists are sequence containers that allow non-contiguous memory allocation. As compared to vector, list has slow traversal, but once a position has been found, insertion and deletion are quick. Syntax: list <Type> name_of_list; Stack are a type of container adaptor wit

Implementing Stack Using Class Templates in C++

The task is to implement some important functions of stack like pop(), push(), display(), topElement(), isEmpty(), isFull() using class template in C++. Stack is a linear data structure that follows a particular order in which the operations are performed. The order may be LIFO(Last In First Out) or

How to implement a Stack using list in C++ STL

In this article, we will discuss how to implement a Stack using list in C++ STL. Stack is a linear data structure which follows. LIFO(Last In First Out) or FILO(First In Last Out). It mainly supports 4 major operations:1. Push: Push an element into the stack.2. Pop: Removes the element by following

Queue using Stacks

Given a stack that supports push and pop operations, your task is to implement a queue using one or more instances of that stack along with its operations.Table of ContentBy Making Enqueue Operation CostlyBy Making Dequeue Operation Costly Queue Implementation Using One Stack and RecursionBy Making