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

An ordered associative container of unique 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_set
    : public /* implementation-defined */::btree_set_container</* implementation-defined */::btree</* implementation-defined */>>
----

== Description

An `absl::btree_set<K>` is an ordered associative container of unique key values designed to be a more efficient replacement for `std::set` (in most cases).

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

An `absl::btree_set<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_set<K, C, A>`.

== Base Classes

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

== Type Aliases

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


== Member Functions

[cols="1,4"]
|===
| Name| Description
| xref:absl/btree_set/2constructor.adoc[`btree_set`]         [.small]#[constructor]#
| Constructs an empty `btree_set`.
| xref:absl/btree_set/emplace-0c.adoc[`emplace`] 
| 
| xref:absl/btree_set/emplace_hint-04.adoc[`emplace_hint`] 
| 
| xref:absl/btree_set/extract-0fa.adoc[`extract`] 
| 
| xref:absl/btree_set/insert-0d.adoc[`insert`] 
| 
| xref:absl/btree_set/merge-0f8.adoc[`merge`] 
| 
|===


== Using Declarations

[cols="1"]
|===
| Name
| xref:absl/btree_set/_10using.adoc[`Unnamed using`] 
| xref:absl/btree_set/begin.adoc[`begin`] 
| xref:absl/btree_set/cbegin.adoc[`cbegin`] 
| xref:absl/btree_set/cend.adoc[`cend`] 
| xref:absl/btree_set/clear.adoc[`clear`] 
| xref:absl/btree_set/contains.adoc[`contains`] 
| xref:absl/btree_set/count.adoc[`count`] 
| xref:absl/btree_set/emplace-04.adoc[`emplace`] 
| xref:absl/btree_set/emplace_hint-0c.adoc[`emplace_hint`] 
| xref:absl/btree_set/empty.adoc[`empty`] 
| xref:absl/btree_set/end.adoc[`end`] 
| xref:absl/btree_set/equal_range.adoc[`equal_range`] 
| xref:absl/btree_set/erase.adoc[`erase`] 
| xref:absl/btree_set/extract-0fc.adoc[`extract`] 
| xref:absl/btree_set/extract_and_get_next.adoc[`extract_and_get_next`] 
| xref:absl/btree_set/find.adoc[`find`] 
| xref:absl/btree_set/get_allocator.adoc[`get_allocator`] 
| xref:absl/btree_set/insert-07.adoc[`insert`] 
| xref:absl/btree_set/key_comp.adoc[`key_comp`] 
| xref:absl/btree_set/lower_bound.adoc[`lower_bound`] 
| xref:absl/btree_set/max_size.adoc[`max_size`] 
| xref:absl/btree_set/merge-02.adoc[`merge`] 
| xref:absl/btree_set/size.adoc[`size`] 
| xref:absl/btree_set/swap.adoc[`swap`] 
| xref:absl/btree_set/upper_bound.adoc[`upper_bound`] 
| xref:absl/btree_set/value_comp.adoc[`value_comp`] 
|===


== Protected Type Aliases

[cols="1"]
|===
| Name
| xref:absl/btree_set/key_arg.adoc[`key_arg`] 
|===


== Non-Member Functions

[cols="1,4"]
|===
| Name| Description
| xref:absl/erase_if-014.adoc[`erase_if`]
| Erases all elements that satisfy the predicate `pred` from the container.
| xref:absl/swap-0ef.adoc[`swap`]
| Swaps the contents of two `absl::btree_set` containers.
|===


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