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std::unorde...t::contains(3) C++ Standard Libary std::unorde...t::contains(3) NAME std::unordered_set::contains - std::unordered_set::contains Synopsis bool contains( const Key& key ) const; (1) (since C++20) template< class K > bool contains( const K& x ) const; (2) (since C++20) 1) Checks if there is an element with key equivalent to key in the container. 2) Checks if there is 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 as- sumes 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 true if there is such an element, otherwise false. Complexity Constant on average, worst case linear in the size of the container. Example // Run this code #include <iostream> #include <unordered_set> int main() { std::unordered_set<int> example = {1, 2, 3, 4}; for(int x: {2, 5}) { if(example.contains(x)) { std::cout << x << ": Found\n"; } else { std::cout << x << ": Not found\n"; } } } Output: 2: Found 5: Not found See also find finds element with specific key (C++11) (public member function) count returns the number of elements matching specific key (C++11) (public member function) equal_range returns range of elements matching a specific key (C++11) (public member function) http://cppreference.com 2022.07.31 std::unorde...t::contains(3)
NAME | Synopsis | Parameters | Return value | Complexity | Example | Output: | See also
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