std::map<Key,T,Compare,Allocator>::count

 

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Containers library

array (C++11)

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std::map

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map::map

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Element access

map::at

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map::beginmap::cbegin (C++11)

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map::rendmap::crend (C++11)

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map::empty

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map::clear

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map::count

map::find

map::contains (C++20)

map::equal_range

map::lower_bound

map::upper_bound

Observers

map::key_comp

map::value_comp

Deduction guides(C++17)

 

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, which is either 1 or 0 since this container does not allow duplicates.

1) Returns the number of elements with key key.

2) Returns the number of elements 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. They allow 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 is either 1 or 0 for (1).

Complexity

Logarithmic in the size of the container.

See also

find	finds element with specific key (public member function)
equal_range	returns range of elements matching a specific key (public member function)