NAME¶

std::set::contains - std::set::contains

Synopsis¶

bool contains( const Key& key ) const; (1) (since C++20)
template< class K > (2) (since C++20)
bool contains( const K& x ) const;

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 the qualified-id
Compare::is_transparent is valid and denotes a type. It 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¶

Logarithmic in the size of the container.

Example¶

// Run this code

#include <iostream>
#include <set>

int main()
{
std::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
(public member function)
count returns the number of elements matching specific key
(public member function)
equal_range returns range of elements matching a specific key
(public member function)