NAME

std::unordered_multimap::contains - std::unordered_multimap::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 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

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_map>

int main()
{
std::unordered_multimap<int,char> example = {{1,'a'},{2,'b'}};

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