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

From cppreference.com

 
 
 
 
iterator find( const Key& key );
(1)
const_iterator find( const Key& key ) const;
(2)
template< class K > iterator find( const K& x );
(3) (since C++20)
template< class K > const_iterator find( const K& x ) const;
(4) (since C++20)
1,2) Finds an element with key equivalent to key.
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.

Parameters

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

Iterator to an element with key equivalent to key. If no such element is found, past-the-end (see end()) iterator is returned.

Complexity

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

Notes

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

Example

#include <iostream>
#include <unordered_map>
 
 
 
int main()
{  
    // simple comparison demo
    std::unordered_multimap<int,char> example = {{1,'a'}, {2,'b'}};
 
    if (auto search = example.find(2); search != example.end())
        std::cout << "Found " << search->first << " " << search->second << '\n';
    else
        std::cout << "Not found\n";
 
 
 
 
}

Output:

Found 2 b

See also

(C++11)
returns the number of elements matching specific key
(public member function)
returns range of elements matching a specific key
(public member function)