std::unordered_multiset<Key,Hash,KeyEqual,Allocator>::count

 

C++

Language

Standard Library Headers

Freestanding and hosted implementations

Named requirements

Language support library

Concepts library (C++20)

Diagnostics library

Utilities library

Strings library

Containers library

Iterators library

Ranges library (C++20)

Algorithms library

Numerics library

Input/output library

Localizations library

Regular expressions library (C++11)

Atomic operations library (C++11)

Thread support library (C++11)

Filesystem library (C++17)

Technical Specifications

 

Containers library

array (C++11)

vector

deque

forward_list (C++11)

list

set

multiset

map

multimap

unordered_set (C++11)

unordered_multiset (C++11)

unordered_map (C++11)

unordered_multimap (C++11)

stack

queue

priority_queue

span (C++20)

 

std::unordered_multiset

Member functions

unordered_multiset::unordered_multiset

unordered_multiset::~unordered_multiset

unordered_multiset::operator=

unordered_multiset::get_allocator

Iterators

unordered_multiset::beginunordered_multiset::cbegin

unordered_multiset::endunordered_multiset::cend

Capacity

unordered_multiset::empty

unordered_multiset::size

unordered_multiset::max_size

Modifiers

unordered_multiset::clear

unordered_multiset::insert

unordered_multiset::emplace

unordered_multiset::emplace_hint

unordered_multiset::erase

unordered_multiset::swap

unordered_multiset::extract (C++17)

unordered_multiset::merge (C++17)

Lookup

unordered_multiset::count

unordered_multiset::find

unordered_multiset::contains (C++20)

unordered_multiset::equal_range

Bucket interface

unordered_multiset::begin(size_type)unordered_multiset::cbegin(size_type)

unordered_multiset::end(size_type)unordered_multiset::cend(size_type)

unordered_multiset::bucket_count

unordered_multiset::max_bucket_count

unordered_multiset::bucket_size

unordered_multiset::bucket

Hash policy

unordered_multiset::load_factor

unordered_multiset::max_load_factor

unordered_multiset::rehash

unordered_multiset::reserve

Observers

unordered_multiset::hash_function

unordered_multiset::key_eq

Non-member functions

operator==operator!= (until C++20)

std::swap

erase_if (C++20)

Deduction guides(C++17)

 

size_type count( const Key& key ) const;	(1)	(since C++11)
template< class K > size_type count( const K& x ) const;	(2)	(since C++20)

1) Returns the number of elements with key that compares equal to the specified argument key.

2) Returns the number of elements with key that compares equivalent to the specified argument x. This overload only participates in overload resolution 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 elements to count
x	-	a value of any type that can be transparently compared with a key

Return value

1) Number of elements with key key.

2) Number of elements with key that compares equivalent to x.

Complexity

linear in the number of elements with key key on average, worst case linear 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)