C++ Map Library - count() Function

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Description

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

Declaration

Following is the declaration for std::multimap::count() function form std::map header.

C++98

size_type count (const key_type& k) const;

Parameters

k − Key for search operation.

Return value

Returns number of values associated with key.

Exceptions

No effect on container if exception is thrown.

Time complexity

Logarithmic i.e. O(log n)

Example

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

#include <iostream>
#include <map>

using namespace std;

int main(void) {
   /* Multimap with duplicates */
   multimap<char, int> m {
         {'a', 1},
         {'a', 2},
         {'b', 3},
         {'c', 4},
         {'c', 5},
               };

   cout << "count of 'a' = " << m.count('a') << endl;
   cout << "count of 'b' = " << m.count('b') << endl;
   cout << "count of 'c' = " << m.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' = 1
count of 'c' = 2