std::unordered_set<Key,Hash,KeyEqual,Allocator>::find
From cppreference.com
< cpp | container | unordered set
| 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: | __cpp_lib_generic_unordered_lookup (for overloads (3,4)) |
Example
Run this code
#include <iostream> #include <unordered_set> int main() { // simple comparison demo std::unordered_set<int> example = {1, 2, 3, 4}; auto search = example.find(2); if (search != example.end()) { std::cout << "Found " << (*search) << '\n'; } else { std::cout << "Not found\n"; } }
Output:
Found 2
See also
| (C++11) |
returns the number of elements matching specific key (public member function) |
| (C++11) |
returns range of elements matching a specific key (public member function) |