std::map<Key,T,Compare,Allocator>::count
From cppreference.com
size_type count( const Key& key ) const; |
(1) | |
template< class K > size_type count( const K& x ) const; |
(2) | (since C++14) |
Returns the number of elements with key that compares equivalent to the specified argument.
1) Returns the number of elements with key key. This is either 1 or 0 since this container does not allow duplicates.
2) Returns the number of elements 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 elements to count |
x | - | alternative value to compare to the keys |
Return value
Number of elements with key that compares equivalent to key or x, which, for overload (1), is either 1 or 0.
Complexity
Logarithmic in the size of the container plus linear in the number of elements found.
Notes
Feature-test macro | Value | Std | Feature |
---|---|---|---|
__cpp_lib_generic_associative_lookup |
201304L | (C++14) | Heterogeneous comparison lookup in associative containers; overload (2) |
Example
This section is incomplete Reason: no example |
See also
finds element with specific key (public member function) | |
returns range of elements matching a specific key (public member function) |