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 Hash::transparent_key_equal is valid and denotes a type. This assumes that such Hash is callable with both K and Key type, and that its key_equal 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

true if there is such an element, otherwise false.

[edit] Complexity

Constant on average, worst case linear in the size of the container.

[edit] Example

#include <iostream>
#include <unordered_set>
int main()
    std::unordered_multiset<int> example = {1, 2, 3, 4};
    if(example.contains(2)) {
        std::cout << "Found\n";
    } else {
        std::cout << "Not found\n";



[edit] See also

finds element with specific key
(public member function) [edit]
returns the number of elements matching specific key
(public member function) [edit]
returns range of elements matching a specific key
(public member function) [edit]