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std::list::empty() function in C++ STL

C++ STL: std::list::empty() function with example: In this tutorial, we will learn to check whether a list is empty or not using list::empty() function.
Submitted by IncludeHelp, on July 02, 2018

C++ STL - std::list::empty() function

empty() is the function of list class, it is used to check whether a list container is empty or not, it returns true (integer value: 1) if list container is empty i.e. its size is 0, otherwise function return false (integer value: 0).

Syntax

list::empty(void);

Parameter(s)

No parameter is passed to the function

Return value

• True (1), if list container is empty
• False (0), if list container is not empty

Sample Input and Output

Input: list list1 {10, 20, 30, 40, 50}
Function calling/validation: list1.empty();
Output: False

Input: list list1 {}
Function calling/validation: list1.empty();
Output: True

Example 1

In this example, there are two lists, list1 has 5 elements and list2 has 0 elements. We have to check whether list containers are empty or not?

#include <iostream>
#include <list>
using namespace std;

int main() {
  // declare and initialize lists
  list<int> list1{10, 20, 30, 40, 50};
  list<int> list2;

  // check list1 is empty or not
  if (list1.empty())
    cout << "list1 is an empty list\n";
  else
    cout << "list1 is not an empty list\n";

  // check list2 is empty or not
  if (list2.empty())
    cout << "list2 is an empty list\n";
  else
    cout << "list2 is not an empty list\n";

  return 0;
}

Output

list1 is not an empty list
list2 is an empty list

Example 2

In this example, there is one list with 5 elements, we have to print its elements by checking till list is not empty i.e. we have to print all elements, and also check if list is empty then returns false.

#include <iostream>
#include <list>
using namespace std;

int main() {
  // declaring list
  list<int> list1{10, 20, 30, 40, 50};

  // printing the elements, if list1 is not empty
  if (!(list1.empty())) {
    cout << "List's elements are:\n";
    while (!(list1.empty())) {
      cout << list1.front() << endl;
      list1.pop_front();
    }
  } else
    cout << "list is empty!!!\n";

  return 0;
}

Output

List's elements are:
10
20
30
40
50