std::unordered_set<Key,Hash,KeyEqual,Allocator>::equal_range

 

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std::unordered_set

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unordered_set::unordered_set unordered_set::~unordered_set unordered_set::operator= unordered_set::get_allocator Iterators unordered_set::beginunordered_set::cbegin unordered_set::endunordered_set::cend Capacity unordered_set::size unordered_set::max_size unordered_set::empty Modifiers unordered_set::clear unordered_set::erase unordered_set::swap unordered_set::extract (C++17) unordered_set::merge (C++17) unordered_set::insert unordered_set::insert_range (C++23)   unordered_set::emplace unordered_set::emplace_hint	Lookup unordered_set::count unordered_set::find unordered_set::contains (C++20) unordered_set::equal_range Bucket interface unordered_set::begin(size_type)unordered_set::cbegin(size_type) unordered_set::end(size_type)unordered_set::cend(size_type) unordered_set::bucket_count unordered_set::max_bucket_count unordered_set::bucket_size unordered_set::bucket Hash policy unordered_set::load_factor unordered_set::max_load_factor unordered_set::rehash unordered_set::reserve Observers unordered_set::hash_function unordered_set::key_eq
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operator==operator!= (until C++20)	std::swap(std::unordered_set) erase_if(std::unordered_set) (C++20)
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std::pair<iterator, iterator> equal_range( const Key& key );	(1)	(since C++11)
std::pair<const_iterator, const_iterator> equal_range( const Key& key ) const;	(2)	(since C++11)
template< class K > std::pair<iterator, iterator> equal_range( const K& x );	(3)	(since C++20)
template< class K > std::pair<const_iterator, const_iterator> equal_range( const K& x ) const;	(4)	(since C++20)

1,2) Returns a range containing all elements with key key in the container. The range is defined by two iterators, the first pointing to the first element of the wanted range and the second pointing past the last element of the range.

3,4) Returns a range containing all elements in the container with key equivalent to 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 to compare the elements to
x	-	a value of any type that can be transparently compared with a key

Return value

std::pair containing a pair of iterators defining the wanted range. If there are no such elements, past-the-end (see end()) iterators are returned as both elements of the pair.

Complexity

Average case linear in the number of elements with the key key, worst case linear in the size of the container.

Notes

Feature-test macro	Value	Std	Feature
__cpp_lib_generic_unordered_lookup	201811L	(C++20)	Heterogeneous comparison lookup in unordered associative containers, overloads (3,4)

See also

find	finds element with specific key (public member function)
contains (C++20)	checks if the container contains element with specific key (public member function)
count	returns the number of elements matching specific key (public member function)
equal_range	returns range of elements matching a specific key (function template)