Difference between revisions of "cpp/container/unordered multiset"

Latest revision as of 15:45, 1 November 2024

Defined in header `<unordered_set>`
template< class Key, class Hash = std::hash<Key>, class KeyEqual = std::equal_to<Key>, class Allocator = std::allocator<Key> > class unordered_multiset;	(1)	(since C++11)
namespace pmr { template< class Key, class Hash = std::hash<Key>, class Pred = std::equal_to<Key> > using unordered_multiset = std::unordered_multiset<Key, Hash, Pred, std::pmr::polymorphic_allocator<Key>>; }	(2)	(since C++17)

std::unordered_multiset is an associative container that contains set of possibly non-unique objects of type Key. Search, insertion, and removal have average constant-time complexity.

Internally, the elements are not sorted in any particular order, but organized into buckets. Which bucket an element is placed into depends entirely on the hash of its value. This allows fast access to individual elements, since once hash is computed, it refers to the exact bucket the element is placed into.

The iteration order of this container is not required to be stable (so, for example, std::equal cannot be used to compare two std::unordered_multisets), except that every group of elements whose keys compare equivalent (compare equal with key_eq() as the comparator) forms a contiguous subrange in the iteration order, also accessible with equal_range().

std::unordered_multiset meets the requirements of Container, AllocatorAwareContainer, UnorderedAssociativeContainer.

Type	Definition
`key_type`	`Key`[edit]
`value_type`	`Key`[edit]
`size_type`	Unsigned integer type (usually std::size_t)[edit]
`difference_type`	Signed integer type (usually std::ptrdiff_t)[edit]
`hasher`	`Hash`[edit]
`key_equal`	`KeyEqual`[edit]
`allocator_type`	`Allocator`[edit]
`reference`	value_type&[edit]
`const_reference`	const value_type&[edit]
`pointer`	std::allocator_traits<Allocator>::pointer[edit]
`const_pointer`	std::allocator_traits<Allocator>::const_pointer[edit]
`iterator`	Constant LegacyForwardIterator to `value_type`[edit]
`const_iterator`	LegacyForwardIterator to const value_type[edit]
`local_iterator`	An iterator type whose category, value, difference, pointer and reference types are the same as `iterator`. This iterator can be used to iterate through a single bucket but not across buckets[edit]
`const_local_iterator`	An iterator type whose category, value, difference, pointer and reference types are the same as `const_iterator`. This iterator can be used to iterate through a single bucket but not across buckets[edit]
`node_type` (since C++17)	a specialization of node handle representing a container node[edit]

[edit] Member functions

(constructor)	constructs the `unordered_multiset` (public member function) [edit]
(destructor)	destructs the `unordered_multiset` (public member function) [edit]
operator=	assigns values to the container (public member function) [edit]
get_allocator	returns the associated allocator (public member function) [edit]
Iterators
begincbegin	returns an iterator to the beginning (public member function) [edit]
endcend	returns an iterator to the end (public member function) [edit]
Capacity
empty	checks whether the container is empty (public member function) [edit]
size	returns the number of elements (public member function) [edit]
max_size	returns the maximum possible number of elements (public member function) [edit]
Modifiers
clear	clears the contents (public member function) [edit]
insert	inserts elements or nodes(since C++17) (public member function) [edit]
insert_range (C++23)	inserts a range of elements (public member function) [edit]
emplace	constructs element in-place (public member function) [edit]
emplace_hint	constructs elements in-place using a hint (public member function) [edit]
erase	erases elements (public member function) [edit]
swap	swaps the contents (public member function) [edit]
extract (C++17)	extracts nodes from the container (public member function) [edit]
merge (C++17)	splices nodes from another container (public member function) [edit]
Lookup
count	returns the number of elements matching specific key (public member function) [edit]
find	finds element with specific key (public member function) [edit]
contains (C++20)	checks if the container contains element with specific key (public member function) [edit]
equal_range	returns range of elements matching a specific key (public member function) [edit]
Bucket interface
begin(size_type)cbegin(size_type)	returns an iterator to the beginning of the specified bucket (public member function) [edit]
end(size_type)cend(size_type)	returns an iterator to the end of the specified bucket (public member function) [edit]
bucket_count	returns the number of buckets (public member function) [edit]
max_bucket_count	returns the maximum number of buckets (public member function) [edit]
bucket_size	returns the number of elements in specific bucket (public member function) [edit]
bucket	returns the bucket for specific key (public member function) [edit]
Hash policy
load_factor	returns average number of elements per bucket (public member function) [edit]
max_load_factor	manages maximum average number of elements per bucket (public member function) [edit]
rehash	reserves at least the specified number of buckets and regenerates the hash table (public member function) [edit]
reserve	reserves space for at least the specified number of elements and regenerates the hash table (public member function) [edit]
Observers
hash_function	returns function used to hash the keys (public member function) [edit]
key_eq	returns the function used to compare keys for equality (public member function) [edit]

[edit] Non-member functions

operator==operator!= (C++11)(C++11)(removed in C++20)	compares the values in the unordered_multiset (function template) [edit]
std::swap(std::unordered_multiset) (C++11)	specializes the std::swap algorithm (function template) [edit]
erase_if(std::unordered_multiset) (C++20)	erases all elements satisfying specific criteria (function template) [edit]

Deduction guides

(since C++17)

[edit] Notes

The member types iterator and const_iterator may be aliases to the same type. This means defining a pair of function overloads using the two types as parameter types may violate the One Definition Rule. Since iterator is convertible to const_iterator, a single function with a const_iterator as parameter type will work instead.

Feature-test macro	Value	Std	Feature
`__cpp_lib_containers_ranges`	202202L	(C++23)	Ranges construction and insertion for containers

[edit] Example

[edit] 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 2050	C++11	the definitions of `reference`, `const_reference`, `pointer` and `const_pointer` were based on `allocator_type`	based on `value_type` and std::allocator_traits

[edit] See also

unordered_set (C++11)	collection of unique keys, hashed by keys (class template) [edit]
multiset	collection of keys, sorted by keys (class template) [edit]
flat_multiset (C++23)	adapts a container to provide a collection of keys, sorted by keys (class template) [edit]

@@ Line 3: / Line 3: @@
 {{dcl begin}}
 {{dcl header|unordered_set}}
-{{dcl|num=1| since=c++11|1=
+{{dcl|num=1|since=c++11|1=
 template<
      class Key,
-     class Hash {{=}} std::hash<Key>,
+     class Hash = std::hash<Key>,
-     class KeyEqual {{=}} std::equal_to<Key>,
+     class KeyEqual = std::equal_to<Key>,
-     class Allocator {{=}} std::allocator<Key>
+     class Allocator = std::allocator<Key>
 > class unordered_multiset;
 }}
 {{dcl|num=2|since=c++17|1=
 namespace pmr {
-     template <class Key,
+     template<
-              class Hash = std::hash<Key>,
+        class Key,
-              class Pred = std::equal_to<Key>>
+        class Hash = std::hash<Key>,
-     using unordered_multiset = std::unordered_multiset<Key, Hash, Pred,
+        class Pred = std::equal_to<Key>
-                                   std::pmr::polymorphic_allocator<Key>>
+     > using unordered_multiset = std::unordered_multiset<Key, Hash, Pred,
+                                     std::pmr::polymorphic_allocator<Key>>;
 }
 }}
 {{dcl end}}
-{{tt|std::unordered_multiset}} es un contenedor asociativo que contiene un conjunto de objetos posiblemente no únicos de tipo {{tt|Key}}. La búsqueda, inserción y eliminación tienen una complejidad promedio de tiempo constante.
+{{tt|std::unordered_multiset}} is an associative container that contains set of possibly non-unique objects of type Key. Search, insertion, and removal have average constant-time complexity.
-Internamente, los elementos no se ordenan en ningún orden en particular, sino que se organizan en grupos. En qué depósito se coloca un elemento depende completamente de la dispersión (''hash'') de su valor. Esto permite un acceso rápido a elementos individuales, ya que una vez que se calcula la dispersión, se refiere al depósito exacto en el que se coloca el elemento.
+Internally, the elements are not sorted in any particular order, but organized into buckets. Which bucket an element is placed into depends entirely on the hash of its value. This allows fast access to individual elements, since once hash is computed, it refers to the exact bucket the element is placed into.
-No se requiere que el orden de iteración de este contenedor sea estable (así que, por ejemplo, {{lc|std::equal}} no puede usarse para comparar dos {{tt|std::unordered_multiset}}s), excepto que cada grupo de elementos cuyas claves se comparan ''equivalentes'' (se comparan iguales con {{lc|key_eq()}} como el comparador) forma un rango contiguo en el orden de iteración, también accesible con {{lc|std::unordered_multiset::equal_range|equal_range()}}.
+The iteration order of this container is not required to be stable (so, for example, {{lc|std::equal}} cannot be used to compare two {{tt|std::unordered_multiset}}s), except that every group of elements whose keys compare ''equivalent'' (compare equal with {{lc|key_eq()}} as the comparator) forms a contiguous subrange in the iteration order, also accessible with {{lc|equal_range()}}.
-{{tt|std::unordered_multiset}} cumple con los requerimientos de {{named req|Container}}, {{named req|AllocatorAwareContainer}}, {{named req|UnorderedAssociativeContainer}}.
+{{tt|std::unordered_multiset}} meets the requirements of {{named req|Container}}, {{named req|AllocatorAwareContainer}}, {{named req|UnorderedAssociativeContainer}}.
-===Tipos miembro===
+===Template parameters===
+{{todo|Add descriptions of the template parameters.}}
+===Member types===
 {{dsc begin}}
-{{dsc hitem | Tipo miembro | Definición}}
+{{dsc hitem|Type|Definition}}
-{{dsc inc | cpp/container/dsc key_type | unordered_multiset}}
+{{dsc inc|cpp/container/dsc key_type|unordered_multiset}}
-{{dsc inc | cpp/container/dsc value_type | unordered_multiset}}
+{{dsc inc|cpp/container/dsc value_type|unordered_multiset}}
-{{dsc inc | cpp/container/dsc size_type | unordered_multiset}}
+{{dsc inc|cpp/container/dsc size_type|unordered_multiset}}
-{{dsc inc | cpp/container/dsc difference_type | unordered_multiset}}
+{{dsc inc|cpp/container/dsc difference_type|unordered_multiset}}
-{{dsc inc | cpp/container/dsc hasher | unordered_multiset}}
+{{dsc inc|cpp/container/dsc hasher|unordered_multiset}}
-{{dsc inc | cpp/container/dsc key_equal | unordered_multiset}}
+{{dsc inc|cpp/container/dsc key_equal|unordered_multiset}}
-{{dsc inc | cpp/container/dsc allocator_type | unordered_multiset}}
+{{dsc inc|cpp/container/dsc allocator_type|unordered_multiset}}
-{{dsc inc | cpp/container/dsc reference | unordered_multiset}}
+{{dsc inc|cpp/container/dsc reference|unordered_multiset}}
-{{dsc inc | cpp/container/dsc const_reference | unordered_multiset}}
+{{dsc inc|cpp/container/dsc const_reference|unordered_multiset}}
-{{dsc inc | cpp/container/dsc pointer | unordered_multiset}}
+{{dsc inc|cpp/container/dsc pointer|unordered_multiset}}
-{{dsc inc | cpp/container/dsc const_pointer | unordered_multiset}}
+{{dsc inc|cpp/container/dsc const_pointer|unordered_multiset}}
-{{dsc inc | cpp/container/dsc iterator | unordered_multiset}}
+{{dsc inc|cpp/container/dsc iterator|unordered_multiset}}
-{{dsc inc | cpp/container/dsc const_iterator | unordered_multiset}}
+{{dsc inc|cpp/container/dsc const_iterator|unordered_multiset}}
-{{dsc inc | cpp/container/dsc local_iterator | unordered_multiset}}
+{{dsc inc|cpp/container/dsc local_iterator|unordered_multiset}}
-{{dsc inc | cpp/container/dsc const_local_iterator | unordered_multiset}}
+{{dsc inc|cpp/container/dsc const_local_iterator|unordered_multiset}}
-{{dsc inc | cpp/container/dsc node_type | unordered_multiset}}
+{{dsc inc|cpp/container/dsc node_type|unordered_multiset}}
 {{dsc end}}
-===Funciones miembro===
+===Member functions===
 {{dsc begin}}
-{{dsc inc | cpp/container/dsc constructor | unordered_multiset}}
+{{dsc inc|cpp/container/dsc constructor|unordered_multiset}}
-{{dsc inc | cpp/container/dsc destructor | unordered_multiset}}
+{{dsc inc|cpp/container/dsc destructor|unordered_multiset}}
-{{dsc inc | cpp/container/dsc operator{{=}} | unordered_multiset}}
+{{dsc inc|cpp/container/dsc operator{{=}}|unordered_multiset}}
-{{dsc inc | cpp/container/dsc get_allocator | unordered_multiset}}
+{{dsc inc|cpp/container/dsc get_allocator|unordered_multiset}}
-{{dsc h2 | Iteradores}}
+{{dsc h2|Iterators}}
-{{dsc inc | cpp/container/dsc begin | unordered_multiset}}
+{{dsc inc|cpp/container/dsc begin|unordered_multiset}}
-{{dsc inc | cpp/container/dsc end | unordered_multiset}}
+{{dsc inc|cpp/container/dsc end|unordered_multiset}}
-{{dsc h2 | Capacidad}}
+{{dsc h2|Capacity}}
-{{dsc inc | cpp/container/dsc empty | unordered_multiset}}
+{{dsc inc|cpp/container/dsc empty|unordered_multiset}}
-{{dsc inc | cpp/container/dsc size | unordered_multiset}}
+{{dsc inc|cpp/container/dsc size|unordered_multiset}}
-{{dsc inc | cpp/container/dsc max_size | unordered_multiset}}
+{{dsc inc|cpp/container/dsc max_size|unordered_multiset}}
-{{dsc h2 | Modificadores}}
+{{dsc h2|Modifiers}}
-{{dsc inc | cpp/container/dsc clear | unordered_multiset}}
+{{dsc inc|cpp/container/dsc clear|unordered_multiset}}
-{{dsc inc | cpp/container/dsc insert | unordered_multiset}}
+{{dsc inc|cpp/container/dsc insert|unordered_multiset}}
-{{dsc inc | cpp/container/dsc emplace | unordered_multiset}}
+{{dsc inc|cpp/container/dsc insert_range|unordered_multiset}}
-{{dsc inc | cpp/container/dsc emplace_hint | unordered_multiset}}
+{{dsc inc|cpp/container/dsc emplace|unordered_multiset}}
-{{dsc inc | cpp/container/dsc erase | unordered_multiset}}
+{{dsc inc|cpp/container/dsc emplace_hint|unordered_multiset}}
-{{dsc inc | cpp/container/dsc swap | unordered_multiset}}
+{{dsc inc|cpp/container/dsc erase|unordered_multiset}}
-{{dsc inc | cpp/container/dsc extract | unordered_multiset}}
+{{dsc inc|cpp/container/dsc swap|unordered_multiset}}
-{{dsc inc | cpp/container/dsc merge | unordered_multiset}}
+{{dsc inc|cpp/container/dsc extract|unordered_multiset}}
+{{dsc inc|cpp/container/dsc merge|unordered_multiset}}
-{{dsc h2 | Búsqueda}}
+{{dsc h2|Lookup}}
-{{dsc inc | cpp/container/dsc count | unordered_multiset}}
+{{dsc inc|cpp/container/dsc count|unordered_multiset}}
-{{dsc inc | cpp/container/dsc find | unordered_multiset}}
+{{dsc inc|cpp/container/dsc find|unordered_multiset}}
-{{dsc inc | cpp/container/dsc contains | unordered_multiset}}
+{{dsc inc|cpp/container/dsc contains|unordered_multiset}}
-{{dsc inc | cpp/container/dsc equal_range | unordered_multiset}}
+{{dsc inc|cpp/container/dsc equal_range|unordered_multiset}}
-{{dsc h2 | Interfaz de depósito}}
+{{dsc h2|Bucket interface}}
-{{dsc inc | cpp/container/dsc begin(int) | unordered_multiset}}
+{{dsc inc|cpp/container/dsc begin(int)|unordered_multiset}}
-{{dsc inc | cpp/container/dsc end(int) | unordered_multiset}}
+{{dsc inc|cpp/container/dsc end(int)|unordered_multiset}}
-{{dsc inc | cpp/container/dsc bucket_count | unordered_multiset}}
+{{dsc inc|cpp/container/dsc bucket_count|unordered_multiset}}
-{{dsc inc | cpp/container/dsc max_bucket_count | unordered_multiset}}
+{{dsc inc|cpp/container/dsc max_bucket_count|unordered_multiset}}
-{{dsc inc | cpp/container/dsc bucket_size | unordered_multiset}}
+{{dsc inc|cpp/container/dsc bucket_size|unordered_multiset}}
-{{dsc inc | cpp/container/dsc bucket | unordered_multiset}}
+{{dsc inc|cpp/container/dsc bucket|unordered_multiset}}
-{{dsc h2 | Política de dispersión}}
+{{dsc h2|Hash policy}}
-{{dsc inc | cpp/container/dsc load_factor | unordered_multiset}}
+{{dsc inc|cpp/container/dsc load_factor|unordered_multiset}}
-{{dsc inc | cpp/container/dsc max_load_factor | unordered_multiset}}
+{{dsc inc|cpp/container/dsc max_load_factor|unordered_multiset}}
-{{dsc inc | cpp/container/dsc rehash | unordered_multiset}}
+{{dsc inc|cpp/container/dsc rehash|unordered_multiset}}
-{{dsc inc | cpp/container/dsc reserve | unordered_multiset}}
+{{dsc inc|cpp/container/dsc reserve|unordered_multiset}}
-{{dsc h2 | Observadores}}
+{{dsc h2|Observers}}
-{{dsc inc | cpp/container/dsc hash_function | unordered_multiset}}
+{{dsc inc|cpp/container/dsc hash_function|unordered_multiset}}
-{{dsc inc | cpp/container/dsc key_eq | unordered_multiset}}
+{{dsc inc|cpp/container/dsc key_eq|unordered_multiset}}
 {{dsc end}}
-===Funciones no miembro===
+===Non-member functions===
 {{dsc begin}}
-{{dsc inc | cpp/container/dsc operator_cmp_unord | unordered_multiset}}
+{{dsc inc|cpp/container/dsc operator_cmp_unord|unordered_multiset}}
-{{dsc inc | cpp/container/dsc swap2 | unordered_multiset}}
+{{dsc inc|cpp/container/dsc swap2|unordered_multiset}}
-{{dsc inc | cpp/container/dsc erase_if | unordered_multiset}}
+{{dsc inc|cpp/container/dsc erase_if|unordered_multiset}}
 {{dsc end}}
-===[[cpp/container/unordered_multiset/deduction_guides|Guías de deducción]]{{mark since c++17}}===
+{{rrev|since=c++17|
+==={{rl|deduction guides|Deduction guides}}===
+}}
-===Notas===
+===Notes===
-{{cpp/container/assoc_note}}
+{{cpp/container/assoc note}}
+{{ftm begin|std=1|comment=1}}
+{{ftm|__cpp_lib_containers_ranges|value=202202L|std=C++23|Ranges construction and insertion for containers}}
+{{ftm end}}
+===Example===
+{{example}}
+===Defect reports===
+{{dr list begin}}
+{{dr list item|wg=lwg|dr=2050|std=C++11|before=the definitions of {{tt|reference}}, {{tt|const_reference}}, {{tt|pointer}}<br>and {{tt|const_pointer}} were based on {{tt|allocator_type}}|after=based on {{tt|value_type}} and<br>{{lc|std::allocator_traits}}}}
+{{dr list end}}
+===See also===
+{{dsc begin}}
+{{dsc inc|cpp/container/dsc unordered_set}}
+{{dsc inc|cpp/container/dsc multiset}}
+{{dsc inc|cpp/container/dsc flat_multiset}}
+{{dsc end}}
-{{langlinks|de|en|fr|it|ja|pt|ru|zh}}
+{{langlinks|de|es|fr|it|ja|pt|ru|zh}}

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Difference between revisions of "cpp/container/unordered multiset"

Latest revision as of 15:45, 1 November 2024

Contents

[edit] Template parameters

[edit] Member types

[edit] Member functions

Iterators

Capacity

Modifiers

Lookup

Bucket interface

Hash policy

Observers