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std::unordered_multiset::find(3) C++ Standard Libary std::unordered_multiset::find(3)


std::unordered_multiset::find - std::unordered_multiset::find


iterator find( const Key& key ); (1) (since C++11)
const_iterator find( const Key& key ) const; (2) (since C++11)
template< class K > (3) (since C++20)
iterator find( const K& x );
template< class K > (4) (since C++20)
const_iterator find( const K& x ) const;

1,2) Finds an element with key equivalent to key. If there are several elements with
the requested key in the container, any of them may be returned.
3,4) Finds an element with key that compares equivalent to the value 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 - key value of the element to search for
x - a value of any type that can be transparently compared with a key

Return value

An iterator to the requested element. If no such element is found, past-the-end (see
end()) iterator is returned.


Constant on average, worst case linear in the size of the container.


Feature-test macro Value Std Feature
Heterogeneous comparison lookup
__cpp_lib_generic_unordered_lookup 201811L (C++20) in unordered associative
containers; overloads (3,4)


// Run this code

#include <iostream>
#include <unordered_set>

int main()
// Simple comparison demo.
std::unordered_multiset<int> example = {1, 2, 3, 4};

if (auto search = example.find(2); search != example.end())
std::cout << "Found " << (*search) << '\n';
std::cout << "Not found\n";


Found 2

See also

count returns the number of elements matching specific key
(public member function)
equal_range returns range of elements matching a specific key
(public member function)