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

The syntax of set::count is:

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.

Complexity Analysis

• Time Complexity: O(log N), where N is the number of elements present in the set.
• Space Complexity: O(1)

Example

The below C++ program demonstrates the use of the count() function in the set container.

C++

// 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

Difference between count() and find()

The difference between count() and find() functions in a set is count() returns 0 or 1 depending upon whether the element is not present or present respectively whereas the find() function returns an iterator pointing to the value if present else next to the last value in the set.