set count() function in C++ STL

The set::count() is a built-in function in C++ STL which returns the number of times an element occurs in the set. It can only return 1 or 0 as the set container contains unique elements only. 
Syntax:

set_name.count(element) 

Parameters: The function accepts one mandatory parameter element which specifies the element whose count is to be returned. 
Return Value: The function returns 1 or 0 as the set contains unique elements only. It returns 1 if the value is present in the set container. It returns 0 if it is not present in the container. 

Time Complexity : Time Complexity for count function is O(log N) where N is the number of elements present in the set

Difference between count and find function in a set is count returns 0 or 1 depending upon whether element is not present or present respectively whereas find function returns a iterator pointing to the value if present else next to the last value in the set.
Below is the illustration of the above function.

CPP

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

    int arr[] = { 14, 12, 15, 11, 10 };

    // initializes the set from an array
    set<int> s(arr, arr + 5);

    // check if 11 is present or not
    if (s.count(11))
        cout << "11 is present in the set\n";
    else
        cout << "11 is not present in the set\n";

    // checks if 18 is present or not
    if (s.count(18))
        cout << "18 is present in the set\n";
    else
        cout << "18 is not present in the set\n";

    return 0;
}

Output:

11 is present in the set
18 is not present in the set

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