unordered_multimap count() function in C++ STL Last Updated : 28 Dec, 2022 Comments Improve Suggest changes Like Article Like Report The unordered_multimap::count() is a built-in function in C++ STL that returns the number of elements in the container whose key is equal to the key passed in the parameter. Syntax: unordered_multimap_name.count(key) Parameters: The function accepts a single mandatory parameter key that specifies the key whose count in the unordered_multimap container is to be returned. Return Value: It returns an unsigned integral type which denotes the number of times a key occurs in the container. Time Complexity: O(N) Below programs illustrates the above function: Program 1: CPP // C++ program to illustrate the // unordered_multimap::count() #include <bits/stdc++.h> using namespace std; int main() { // declaration unordered_multimap<int, int> sample; // inserts key and element sample.insert({ 10, 100 }); sample.insert({ 10, 100 }); sample.insert({ 20, 200 }); sample.insert({ 30, 300 }); sample.insert({ 30, 150 }); cout << "10 occurs " << sample.count(10) << " times"; cout << "\n20 occurs " << sample.count(20) << " times"; cout << "\n13 occurs " << sample.count(13) << " times"; cout << "\n30 occurs " << sample.count(30) << " times"; return 0; } Output:10 occurs 2 times 20 occurs 1 times 13 occurs 0 times 30 occurs 2 times Program 2: CPP // C++ program to illustrate the // unordered_multimap::count() #include <bits/stdc++.h> using namespace std; int main() { // declaration unordered_multimap<char, char> sample; // inserts key and element sample.insert({ 'a', 'b' }); sample.insert({ 'a', 'b' }); sample.insert({ 'b', 'c' }); sample.insert({ 'r', 'a' }); sample.insert({ 'r', 'b' }); cout << "a occurs " << sample.count('a') << " times"; cout << "\nb occurs " << sample.count('b') << " times"; cout << "\nz occurs " << sample.count('z') << " times"; cout << "\nr occurs " << sample.count('r') << " times"; return 0; } Output:a occurs 2 times b occurs 1 times z occurs 0 times r occurs 2 times Comment More infoAdvertise with us Next Article unordered_multimap clear() function in C++ STL G gopaldave Follow Improve Article Tags : Misc C++ STL CPP-Functions cpp-unordered_multimap +1 More Practice Tags : CPPMiscSTL Similar Reads Unordered Multimap in C++ STL In C++, the unordered_multimap is an unordered associative container that stores data in the form of key-value pairs. It is similar to unordered map, but it allows multiple elements with the same key. It provides fast insertion, deletion and search operations in O(1) time by using hashing.Example:C+ 7 min read unordered_multimap begin() and end() function in C++ STL The unordered_multimap::begin() is a built-in function in C++ STL that returns an iterator pointing to the first element in the container or to the first element in one of its buckets. Syntax: unordered_multimap_name.begin(n) Parameters: The function accepts one parameter. If a parameter is passed, 5 min read unordered_multimap size() function in C++ STL The unordered_multimap::size() is a built-in function in C++ STL which returns the size of the unordered_multimap. It denotes the number of elements in that container. Syntax: unordered_multimap_name.size() Parameters: The function does not accept any parameters. Return Value: It returns an integral 3 min read unordered_multimap empty() function in C++ STL The unordered_multimap::empty() is a built-in function in C++ STL which returns a boolean value. It returns true if the unordered_multimap container is empty. Otherwise, it returns false. Syntax: unordered_multimap_name.empty() Parameters: The function does not accept any parameter. Return Value: It 2 min read unordered_multimap insert() in C++ STL The function std::unordered_multimap::insert() is a built-in function in C++ STL that extends container by inserting new element in unordered_multimap. This function increases container size by one. The insert() function can be used to insert a single key-value pair, a complete unordered_map, initia 2 min read unordered_multimap emplace() function in C++ STL The unordered_multimap::emplace() is a built-in function in C++ STL which inserts a new {key, element} in the unordered_multimap container. The insertion is done automatically at the position according to the container's criterion. It increases the size of the container by one. Syntax: unordered_mul 2 min read unordered_multimap find() function in C++ STL The unordered_multimap::find() is a built-in function in C++ STL which returns an iterator which points to one of the elements which has the key k. If the container does not contain any element with key k, then it returns an iterator which points to the position which is past the last element in the 3 min read unordered_multimap count() function in C++ STL The unordered_multimap::count() is a built-in function in C++ STL that returns the number of elements in the container whose key is equal to the key passed in the parameter. Syntax: unordered_multimap_name.count(key) Parameters: The function accepts a single mandatory parameter key that specifies th 2 min read unordered_multimap clear() function in C++ STL The unordered_multimap::clear() is a built-in function in C++ STL which clears the contents of the unordered_multimap container. The final size of the container after the call of the function is 0. Syntax: unordered_multimap_name.clear() Parameters: The function does not accept any parameter. Return 2 min read unordered_multimap swap() function in C++ STL The unordered_multimap::swap() is a built-in function in C++ STL which swaps the contents of two unordered_multimap containers. The sizes can differ of both the containers. Syntax: unordered_multimap_name1.swap(unordered_multimap_name2) Parameters: The function accepts a single mandatory parameter u 3 min read Like