list empty() function in C++ STL

The list::empty() is a built-in function in C++ STL that is used to check whether a particular list container is empty or not. This function does not modify the list, it simply checks whether a list is empty or not, i.e. the size of the list is zero or not.

Syntax

list_name.empty() 

Parameters

• This function does not accept any parameter, it simply checks whether a list container is empty or not.

Return Value

• The return type of this function is boolean.
• It returns True is the size of the list container is zero otherwise it returns False.

Example

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

C++

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

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

    // check if list is empty
    if (demoList.empty())
        cout << "Empty List\n";
    else
        cout << "Not Empty\n";

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

    // check again if list is empty
    if (demoList.empty())
        cout << "Empty List\n";
    else
        cout << "Not Empty\n";

    return 0;
}

Output

Empty List
Not Empty

Time Complexity: O(1)
Space Complexity: O(1)

Note: This function works in constant time complexity.