std::unordered_multiset<Key,Hash,KeyEqual,Allocator>::count

Since C++11

Returns the number of elements with key that compares equal to the specified argument key.

# Declarations

size_type count( const Key& key ) const;

(since C++11)

template< class K >
size_type count( const K& x ) const;

(since C++20)

# Parameters

key: key value of the elements to count
x: a value of any type that can be transparently compared with a key

# Notes

Feature-test macro Value Std Feature __cpp_lib_generic_unordered_lookup 201811L (C++20) Heterogeneous comparison lookup in unordered associative containers, overload (2)

# Example

#include <algorithm>
#include <iostream>
#include <unordered_set>
 
int main()
{
    std::unordered_multiset set{2, 7, 1, 8, 2, 8, 1, 8, 2, 8};
 
    std::cout << "The set is:\n";
    for (int e : set)
        std::cout << e << ' ';
 
    const auto [min, max] = std::ranges::minmax(set);
 
    std::cout << "\nNumbers [" << min << ".." << max << "] frequency:\n";
 
    for (int i{min}; i <= max; ++i)
        std::cout << i << ':' << set.count(i) << "; ";
    std::cout << '\n';
}