std::set<Key,Compare,Allocator>::contains (3) - Linux Manuals
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 only participates in overload resolution if the qualified-id Compare::is_transparent is valid and denotes a type. It allows calling this function without constructing an instance of Key.
key - key value of the element to search for
x - a value of any type that can be transparently compared with a key
true if there is such an element, otherwise false.
Logarithmic in the size of the container.
// Run this code
find (public member function)
count (public member function)
equal_range (public member function)