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

 

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unordered_set (C++11)

unordered_multiset (C++11)

unordered_map (C++11)

unordered_multimap (C++11)

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std::unordered_multiset

Member types
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::size unordered_multiset::max_size unordered_multiset::empty Modifiers unordered_multiset::clear unordered_multiset::insert unordered_multiset::insert_range (C++23) 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(std::unordered_multiset) erase_if(std::unordered_multiset) (C++20)
Deduction guides (C++17)

 

	(1)
unordered_multiset()     : unordered_multiset(size_type(/* implementation-defined */)) {}			(since C++11) (until C++20)
unordered_multiset();			(since C++20)
explicit unordered_multiset( size_type bucket_count,                              const Hash& hash = Hash(),                              const key_equal& equal = key_equal(),                              const Allocator& alloc = Allocator() );		(2)	(since C++11)
unordered_multiset( size_type bucket_count,                     const Allocator& alloc )     : unordered_multiset(bucket_count, Hash(), key_equal(), alloc) {}		(3)	(since C++14)
unordered_multiset( size_type bucket_count,                     const Hash& hash,                     const Allocator& alloc )     : unordered_multiset(bucket_count, hash, key_equal(), alloc) {}		(4)	(since C++14)
explicit unordered_multiset( const Allocator& alloc );		(5)	(since C++11)
template< class InputIt > unordered_multiset( InputIt first, InputIt last,                     size_type bucket_count = /* implementation-defined */,                     const Hash& hash = Hash(),                     const key_equal& equal = key_equal(),                     const Allocator& alloc = Allocator() );		(6)	(since C++11)
template< class InputIt > unordered_multiset( InputIt first, InputIt last,                     size_type bucket_count,                     const Allocator& alloc )     : unordered_multiset(first, last,                          bucket_count, Hash(), key_equal(), alloc) {}		(7)	(since C++14)
template< class InputIt > unordered_multiset( InputIt first, InputIt last,                     size_type bucket_count,                     const Hash& hash,                     const Allocator& alloc )     : unordered_multiset(first, last,                          bucket_count, hash, key_equal(), alloc) {}		(8)	(since C++14)
unordered_multiset( const unordered_multiset& other );		(9)	(since C++11)
unordered_multiset( const unordered_multiset& other, const Allocator& alloc );		(10)	(since C++11)
unordered_multiset( unordered_multiset&& other );		(11)	(since C++11)
unordered_multiset( unordered_multiset&& other, const Allocator& alloc );		(12)	(since C++11)
unordered_multiset( std::initializer_list<value_type> init,                     size_type bucket_count = /* implementation-defined */,                     const Hash& hash = Hash(),                     const key_equal& equal = key_equal(),                     const Allocator& alloc = Allocator() );		(13)	(since C++11)
unordered_multiset( std::initializer_list<value_type> init,                     size_type bucket_count,                     const Allocator& alloc )     : unordered_multiset(init, bucket_count,                          Hash(), key_equal(), alloc) {}		(14)	(since C++14)
unordered_multiset( std::initializer_list<value_type> init,                     size_type bucket_count,                     const Hash& hash,                     const Allocator& alloc )     : unordered_multiset(init, bucket_count,                          hash, key_equal(), alloc) {}		(15)	(since C++14)
template< container-compatible-range<value_type> R > unordered_multiset( std::from_range_t, R&& rg,                     size_type bucket_count = /* see description */,                     const Hash& hash = Hash(),                     const key_equal& equal = key_equal(),                     const Allocator& alloc = Allocator() );		(16)	(since C++23)
template< container-compatible-range<value_type> R > unordered_multiset( std::from_range_t, R&& rg,                     size_type bucket_count,                     const Allocator& alloc )     : unordered_multiset(std::from_range, std::forward<R>(rg),                          bucket_count, Hash(), key_equal(), alloc) {}		(17)	(since C++23)
template< container-compatible-range<value_type> R > unordered_multiset( std::from_range_t, R&& rg,                     size_type bucket_count,                     const Hash& hash,                     const Alloc& alloc )     : unordered_multiset(std::from_range, std::forward<R>(rg),                          bucket_count, hash, key_equal(), alloc) {}		(18)	(since C++23)

Constructs new container from a variety of data sources. Optionally uses user supplied bucket_count as a minimal number of buckets to create, hash as the hash function, equal as the function to compare keys and alloc as the allocator.

1-5) Constructs empty container. Sets max_load_factor() to 1.0. For the default constructor, the number of buckets is implementation-defined.

6-8) Constructs the container with the contents of the range [first, last). Sets max_load_factor() to 1.0.

9,10) Copy constructor. Constructs the container with the copy of the contents of other, copies the load factor, the predicate, and the hash function as well. If alloc is not provided, allocator is obtained by calling std::allocator_traits<allocator_type>::select_on_container_copy_construction(other.get_allocator()).

The template parameter Allocator is only deduced from the first argument while used in class template argument deduction.

(since C++23)

11,12) Move constructor. Constructs the container with the contents of other using move semantics. If alloc is not provided, allocator is obtained by move-construction from the allocator belonging to other.

The template parameter Allocator is only deduced from the first argument while used in class template argument deduction.

(since C++23)

13-15) Initializer-list constructor. Constructs the container with the contents of the initializer list init, same as unordered_multiset(init.begin(), init.end()).

16-18) Constructs the container with the contents of rg.

Parameters

alloc	-	allocator to use for all memory allocations of this container
bucket_count	-	minimal number of buckets to use on initialization. If it is not specified, implementation-defined default value is used
hash	-	hash function to use
equal	-	comparison function to use for all key comparisons of this container
first, last	-	the range [first, last) to copy the elements from
rg	-	a container compatible range, that is, an input_range whose elements are convertible to value_type
other	-	another container to be used as source to initialize the elements of the container with
init	-	initializer list to initialize the elements of the container with
Type requirements
- InputIt must meet the requirements of LegacyInputIterator.

Complexity

1-5) Constant.

6-8) Average case linear (i.e. O(N), where N is std::distance(first, last)), worst case quadratic, i.e. O(N²).

9,10) Linear in size of other.

11,12) Constant. If alloc is given and alloc != other.get_allocator(), then linear.

13-15) Average case O(N) (N is std::size(init)), worst case O(N²).

16-18) Average case O(N) (N is ranges::distance(rg)), worst case O(N²).

Exceptions

Calls to Allocator::allocate may throw.

Notes

After container move construction (overload (4)), references, pointers, and iterators (other than the end iterator) to other remain valid, but refer to elements that are now in *this. The current standard makes this guarantee via the blanket statement in [container.reqmts]/67, and a more direct guarantee is under consideration via LWG issue 2321.

Although not formally required until C++23, some implementations have already put the template parameter Allocator into non-deduced contexts in earlier modes.

Feature-test macro	Value	Std	Feature
__cpp_lib_containers_ranges	202202L	(C++23)	Ranges-aware construction and insertion; overloads (16-18)

Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

DR	Applied to	Behavior as published	Correct behavior
LWG 2193	C++11	the default constructor (1) was explicit	made non-explicit

See also

operator=

assigns values to the container (public member function)