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

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std::map

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map::map
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operator==operator<=> (C++20)
std::swap(std::map)
erase_if(std::map) (C++20)

operator!=operator<operator>operator<=operator>=

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size_type count(const Key& key)const;	(1)	(constexpr since C++26)
template<class K> size_type count(const K& x)const;	(2)	(since C++14) (constexpr since C++26)

Returns the number of elements with key that compares equivalent to the specified argument.

1) Returns the number of elements with keykey.This is either1 or0 since keys are always unique.

2) Returns the number of elements with key that compares equivalent tox.

This overload participates in overload resolution only ifCompare istransparent. It allows calling this function without constructing an instance ofKey.

[edit]Parameters

key	-	key value of the elements to count
x	-	alternative value to compare to the keys

[edit]Return value

Number of elements with key that compares equivalent tokey orx.

[edit]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 inassociative containers; overload(2)

[edit]Example

This section is incomplete
Reason: no example

[edit]See also

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