list front() function in C++ STL

Last Updated : 29 May, 2023

The list::front() is a built-in function in C++ STL which is used to return a reference to the first element in a list container. Unlike the list::begin() function, this function returns a direct reference to the first element in the list container.

Syntax

list_name.front();

Parameters

This function does not accept any parameter, it simply returns a reference to the first element in the list container.

Return Value

This function returns a direct reference to the first element in the list container.

Exception

This function creates an undefined behavior when used with an empty list container.

Example

The below program illustrates the list::front() function.

C++

// CPP program to illustrate the
// list::front() function
#include <bits/stdc++.h>
using namespace std;

int main()
{
    // Creating a list
    list<int> demoList;

    // Add elements to the List
    demoList.push_back(10);
    demoList.push_back(20);
    demoList.push_back(30);
    demoList.push_back(40);

    // get the first element using front()
    int ele = demoList.front();

    // Print the first element
    cout << ele;

    return 0;
}

Output

Time complexity: O(1)
Auxiliary Space: O(n) where n is the size of the list

Note: This function works in constant time complexity.

list back() function in C++ STL

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