std::unordered_multimap<Key,T,Hash,KeyEqual,Allocator>:: count

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

2) Returns the number of elements with key that compares equivalent to the specified argument x . This overload participates in overload resolution only if Hash :: is_transparent and KeyEqual :: is_transparent are valid and each denotes a type. This assumes that such Hash is callable with both K and Key type, and that the KeyEqual is transparent, which, together, allows calling this function without constructing an instance of Key .

1) Number of elements with key key .

2) Number of elements with key that compares equivalent to x .

#include <iostream>
#include <string>
#include <unordered_map>
 
int main()
{
    std::unordered_multimap<int, std::string> dict = {
        {1, "one"}, {6, "six"}, {3, "three"}
    };
    dict.insert({4, "four"});
    dict.insert({5, "five"});
    dict.insert({6, "six"});
 
    std::cout << "dict: { ";
    for (auto const& [key, value] : dict)
        std::cout << '[' << key << "]=" << value << ' ';
    std::cout << "}\n\n";
 
    for (int i{1}; i != 8; ++i)
        std::cout << "dict.count(" << i << ") = " << dict.count(i) << '\n';
}

dict: { [5]=five [4]=four [1]=one [6]=six [6]=six [3]=three }
 
dict.count(1) = 1
dict.count(2) = 0
dict.count(3) = 1
dict.count(4) = 1
dict.count(5) = 1
dict.count(6) = 2
dict.count(7) = 0