unordered_multiset size() in C++ STL

The size() method of unordered_multiset is used to count the number of elements of unordered_set it is called with. It takes the number of elements in the container and counts the number of elements.

Syntax:

size_type size() const;

where size_type is an unsigned integral type.

Return Value: This function returns the length of the controlled sequence or in short, it returns the number of elements in the container.

Below program illustrate the unordered_multiset size() function :-

Example :

#include <iostream>
#include <unordered_set>

using namespace std;

int main()
{

    // Define the unordered_set
    unordered_multiset<int> numbers{ 1, 2, 3, 4, 5, 6 };

    // Calculate and print
    // the size of the unordered_multiset
    cout << "The container has "
         << numbers.size()
         << " elements in it";
}

Output:

The container has 6 elements in it

Complexity :
It takes constant(O(1)) time of complexity to perform an operation.