Difference between revisions of "cpp/container/unordered multiset/find"
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< cpp | container | unordered multiset
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Latest revision as of 07:39, 4 December 2021
| iterator find( const Key& key ); |
(1) | (since C++11) |
| const_iterator find( const Key& key ) const; |
(2) | (since C++11) |
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. 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.Contents |
[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_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'; else std::cout << "Not found\n"; }
Output:
Found 2
[edit] See also
| returns the number of elements matching specific key (public member function) | |
| returns range of elements matching a specific key (public member function) |
