C++ Unordered_multimap Library - count() Function

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Description

The C++ function std::unordered_multimap::count() returns the number of mapped values associated with key k.

Declaration

Following is the declaration for std::unordered_multimap::count() function form std::unordered_map() header.

C++11

size_type count(const key_type& k) const;

Parameters

k − Key for search operation.

Return value

Returns number of values associated with key.

Time complexity

Linear i.e. O(n)

Example

The following example shows the usage of std::unordered_multimap::count() function.

#include <iostream>
#include <unordered_map>

using namespace std;

int main(void) {
   unordered_multimap<char, int> umm = {
            {'a', 1},
            {'a', 2},
            {'b', 3},
            {'b', 4},
            {'c', 5}
            };

   cout << "Count of a = " << umm.count('a') << endl;
   cout << "Count of b = " << umm.count('b') << endl;
   cout << "Count of c = " << umm.count('c') << endl;

   return 0;
}

Let us compile and run the above program, this will produce the following result −

Count of a = 2
Count of b = 2
Count of c = 1