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
10
Time complexity: O(1)
Auxiliary Space: O(n) where n is the size of the list
Note: This function works in constant time complexity.