multiset count() function in C++ STL

The multiset::count() function is a built-in function in C++ STL that searches for a specific element in the multiset container and returns the number of occurrences of that element. 

Syntax: 

multiset_name.count(val)

Parameters: The function accepts a single parameter val which specifies the element to be searched in the multiset container. 

Return Value: The function returns the count of elements which is equal to val in the multiset container. 

Below programs illustrates the multiset::count() function: 

Program 1:

C++

// C++ program to demonstrate the
// multiset::count() function
#include <bits/stdc++.h>
using namespace std;
int main()
{

    int arr[] = { 15, 10, 15, 11, 10, 18, 18, 20, 20 };

    // initializes the set from an array
    multiset<int> s(arr, arr + 9);

    cout << "15 occurs " << s.count(15)
         << " times in container";

    return 0;
}

Output:

15 occurs 2 times in container

Program 2: 

C++

// C++ program to demonstrate the
// multiset::count() function
#include <bits/stdc++.h>
using namespace std;
int main()
{

    int arr[] = { 15, 10, 15, 11, 10, 18, 18, 18, 18 };

    // initializes the set from an array
    multiset<int> s(arr, arr + 9);

    cout << "18 occurs " << s.count(18)
         << " times in container";

    return 0;
}

Output:

18 occurs 4 times in container

The time complexity of the multiset::count() function is O(K + log(N)), where K is the total count of integers of the value passed.