[#absl-btree_multiset]
= xref:absl.adoc[absl]::btree_multiset
:relfileprefix: ../
:mrdocs:

An ordered associative container of keys that allows equivalent keys.

== Synopsis

Declared in `<absl/container/btree_set.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
template<
    typename Key,
    typename Compare = std::less<Key>,
    typename Alloc = std::allocator<Key>>
class btree_multiset
    : public /* implementation-defined */::btree_multiset_container</* implementation-defined */::btree</* implementation-defined */>>
----

== Description

An `absl::btree_multiset<K>` is an ordered associative container of keys and associated values designed to be a more efficient replacement for `std::multiset` (in most cases). Unlike `absl::btree_set`, a B‐tree multiset allows equivalent elements.

Keys are sorted using an (optional) comparison function, which defaults to `std::less<K>`.

An `absl::btree_multiset<K>` uses a default allocator of `std::allocator<K>` to allocate (and deallocate) nodes, and construct and destruct values within those nodes. You may instead specify a custom allocator `A` (which in turn requires specifying a custom comparator `C`) as in `absl::btree_multiset<K, C, A>`.

== Base Classes

[cols="1,4"]
|===
| Name| Description
| `/* implementation-defined */::btree_multiset_container</* implementation-defined */::btree</* implementation-defined */>>`
| 
|===

== Type Aliases

[cols="1"]
|===
| Name
| xref:absl/btree_multiset/allocator_type.adoc[`allocator_type`] 
| xref:absl/btree_multiset/const_iterator.adoc[`const_iterator`] 
| xref:absl/btree_multiset/iterator.adoc[`iterator`] 
| xref:absl/btree_multiset/key_compare.adoc[`key_compare`] 
| xref:absl/btree_multiset/key_type.adoc[`key_type`] 
| xref:absl/btree_multiset/node_type.adoc[`node_type`] 
| xref:absl/btree_multiset/size_type.adoc[`size_type`] 
| xref:absl/btree_multiset/value_type.adoc[`value_type`] 
|===


== Member Functions

[cols="1,4"]
|===
| Name| Description
| xref:absl/btree_multiset/2constructor.adoc[`btree_multiset`]         [.small]#[constructor]#
| Constructs an empty `btree_multiset`.
| xref:absl/btree_multiset/emplace-06.adoc[`emplace`] 
| 
| xref:absl/btree_multiset/emplace_hint-0e.adoc[`emplace_hint`] 
| 
| xref:absl/btree_multiset/extract-08.adoc[`extract`] 
| 
| xref:absl/btree_multiset/insert-0e.adoc[`insert`] 
| 
| xref:absl/btree_multiset/merge-05.adoc[`merge`] 
| 
|===


== Using Declarations

[cols="1"]
|===
| Name
| xref:absl/btree_multiset/_10using.adoc[`Unnamed using`] 
| xref:absl/btree_multiset/begin.adoc[`begin`] 
| xref:absl/btree_multiset/cbegin.adoc[`cbegin`] 
| xref:absl/btree_multiset/cend.adoc[`cend`] 
| xref:absl/btree_multiset/clear.adoc[`clear`] 
| xref:absl/btree_multiset/contains.adoc[`contains`] 
| xref:absl/btree_multiset/count.adoc[`count`] 
| xref:absl/btree_multiset/emplace-0c.adoc[`emplace`] 
| xref:absl/btree_multiset/emplace_hint-06.adoc[`emplace_hint`] 
| xref:absl/btree_multiset/empty.adoc[`empty`] 
| xref:absl/btree_multiset/end.adoc[`end`] 
| xref:absl/btree_multiset/equal_range.adoc[`equal_range`] 
| xref:absl/btree_multiset/erase.adoc[`erase`] 
| xref:absl/btree_multiset/extract-0c.adoc[`extract`] 
| xref:absl/btree_multiset/extract_and_get_next.adoc[`extract_and_get_next`] 
| xref:absl/btree_multiset/find.adoc[`find`] 
| xref:absl/btree_multiset/get_allocator.adoc[`get_allocator`] 
| xref:absl/btree_multiset/insert-07f.adoc[`insert`] 
| xref:absl/btree_multiset/key_comp.adoc[`key_comp`] 
| xref:absl/btree_multiset/lower_bound.adoc[`lower_bound`] 
| xref:absl/btree_multiset/max_size.adoc[`max_size`] 
| xref:absl/btree_multiset/merge-03.adoc[`merge`] 
| xref:absl/btree_multiset/size.adoc[`size`] 
| xref:absl/btree_multiset/swap.adoc[`swap`] 
| xref:absl/btree_multiset/upper_bound.adoc[`upper_bound`] 
| xref:absl/btree_multiset/value_comp.adoc[`value_comp`] 
|===


== Non-Member Functions

[cols="1,4"]
|===
| Name| Description
| xref:absl/erase_if-042.adoc[`erase_if`]
| Erases all elements that satisfy the predicate `pred` from the container.
| xref:absl/swap-06.adoc[`swap`]
| Swaps the contents of two `absl::btree_multiset` containers.
|===


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