std::unordered_multimap<Key,T,Hash,KeyEqual,Allocator>::find
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Tables
std::unordered_multimap (C++23)
(C++17)
(C++17)
unordered_multimap::find
(C++20)
(until C++20)
iterator find( const Key& key );
(1)
(since C++11) (constexpr since C++26)
const_iterator find( const Key& key ) const;
(2)
(since C++11) (constexpr since C++26)
template< class K >
iterator find( const K& x );
(3)
(since C++20) iterator find( const K& x );
(constexpr since C++26)
template< class K >
const_iterator find( const K& x ) const;
(4)
(since C++20) const_iterator find( const K& x ) const;
(constexpr since C++26)
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 x.
This overload participates in overload resolution only if
Hash and KeyEqual are both transparent. 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.[edit] Parameters
key
-
key value of the element to search for
x
-
a value of any type that can be transparently compared with a key
[edit] Return value
An iterator to the requested element. If no such element is found, past-the-end (see end() ) iterator is returned.
[edit] Complexity
Constant on average, worst case linear in the size of the container.
Notes
| Feature-test macro | Value | Std | Feature |
|---|---|---|---|
__cpp_lib_generic_unordered_lookup |
201811L |
(C++20) | Heterogeneous comparison lookup in unordered associative containers; overloads (3,4) |
[edit] Example
Run this code
#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