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

An ordered associative container of keys and associated values that allows equivalent keys.

== Synopsis

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

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

== Description

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

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

An `absl::btree_multimap<K, V>` uses a default allocator of `std::allocator<std::pair<const K, V>>` 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_multimap<K, V, C, A>`.

== Base Classes

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

== Type Aliases

[cols="1"]
|===
| Name
| xref:absl/btree_multimap/mapped_type.adoc[`mapped_type`] 
|===


== Member Functions

[cols="1,4"]
|===
| Name| Description
| xref:absl/btree_multimap/2constructor.adoc[`btree_multimap`]         [.small]#[constructor]#
| Constructs an empty `btree_multimap`.
|===


== Using Declarations

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


== Non-Member Functions

[cols="1,4"]
|===
| Name| Description
| xref:absl/erase_if-0ff.adoc[`erase_if`]
| Erases all elements that satisfy the predicate `pred` from the container.
| xref:absl/swap-000.adoc[`swap`]
| Swaps the contents of two `absl::btree_multimap` containers.
|===


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