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

A simple insertion‐ordered set.

== Synopsis

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

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
template<
    typename Key,
    typename KeyHash = absl::flat_hash_set<Key>::hasher,
    typename KeyEq = absl::flat_hash_set<Key, KeyHash>::key_equal,
    typename Alloc = std::allocator<Key>>
class linked_hash_set;
----

== Description

Provides O(1) amortized insertions and lookups, as well as iteration over the set in the insertion order. This class is thread‐compatible but NOT exception‐safe, and it supports heterogeneous lookups.

== Type Aliases

[cols="1,4"]
|===
| Name| Description
| xref:absl/linked_hash_set/allocator_type.adoc[`allocator_type`] 
| The allocator type.
| xref:absl/linked_hash_set/const_iterator.adoc[`const_iterator`] 
| The const iterator type, iterating in insertion order.
| xref:absl/linked_hash_set/const_pointer.adoc[`const_pointer`] 
| A const pointer to an element.
| xref:absl/linked_hash_set/const_reference.adoc[`const_reference`] 
| A const reference to an element.
| xref:absl/linked_hash_set/const_reverse_iterator.adoc[`const_reverse_iterator`] 
| The const reverse iterator type.
| xref:absl/linked_hash_set/difference_type.adoc[`difference_type`] 
| The signed integer difference type.
| xref:absl/linked_hash_set/hasher.adoc[`hasher`] 
| The hash functor type.
| xref:absl/linked_hash_set/insert_return_type.adoc[`insert_return_type`] 
| The return type of node‐handle insertions.
| xref:absl/linked_hash_set/iterator.adoc[`iterator`] 
| The iterator type, iterating in insertion order.
| xref:absl/linked_hash_set/key_equal.adoc[`key_equal`] 
| The key equality functor type.
| xref:absl/linked_hash_set/key_type.adoc[`key_type`] 
| The key type of the set.
| xref:absl/linked_hash_set/node_type.adoc[`node_type`] 
| The node handle type used to extract and reinsert elements.
| xref:absl/linked_hash_set/pointer.adoc[`pointer`] 
| A pointer to an element.
| xref:absl/linked_hash_set/reference.adoc[`reference`] 
| A reference to an element.
| xref:absl/linked_hash_set/reverse_iterator.adoc[`reverse_iterator`] 
| The reverse iterator type.
| xref:absl/linked_hash_set/size_type.adoc[`size_type`] 
| The unsigned integer size type.
| xref:absl/linked_hash_set/value_type.adoc[`value_type`] 
| The value type stored in the set.
|===


== Member Functions

[cols="1,4"]
|===
| Name| Description
| xref:absl/linked_hash_set/2constructor-0168.adoc[`linked_hash_set`]         [.small]#[constructor]#
| Constructors
| xref:absl/linked_hash_set/operator_assign-06.adoc[`operator=`] 
| Assignment operators
| xref:absl/linked_hash_set/back-0f4.adoc[`back`] 
| `back` overloads
| xref:absl/linked_hash_set/begin-0c.adoc[`begin`] 
| `begin` overloads
| xref:absl/linked_hash_set/bucket_count.adoc[`bucket_count`] 
| Returns the number of buckets in the underlying hash set.
| xref:absl/linked_hash_set/capacity.adoc[`capacity`] 
| Returns the number of elements the set can hold without rehashing.
| xref:absl/linked_hash_set/cbegin.adoc[`cbegin`] 
| Returns a const iterator to the first element, in insertion order.
| xref:absl/linked_hash_set/cend.adoc[`cend`] 
| Returns a const iterator past the last element.
| xref:absl/linked_hash_set/clear.adoc[`clear`] 
| Removes all elements from the set.
| xref:absl/linked_hash_set/contains.adoc[`contains`] 
| Returns whether the set contains an element with the given key.
| xref:absl/linked_hash_set/count.adoc[`count`] 
| Returns the number of elements matching the given key.
| xref:absl/linked_hash_set/crbegin.adoc[`crbegin`] 
| Returns a const reverse iterator to the last element.
| xref:absl/linked_hash_set/crend.adoc[`crend`] 
| Returns a const reverse iterator past the first element.
| xref:absl/linked_hash_set/emplace.adoc[`emplace`] 
| Constructs an element in place in the set.
| xref:absl/linked_hash_set/emplace_hint.adoc[`emplace_hint`] 
| Constructs an element in place in the set using a position hint.
| xref:absl/linked_hash_set/empty.adoc[`empty`] 
| Returns whether the set is empty.
| xref:absl/linked_hash_set/end-0c6.adoc[`end`] 
| `end` overloads
| xref:absl/linked_hash_set/equal_range-055.adoc[`equal_range`] 
| Returns the range of elements matching the given key.
| xref:absl/linked_hash_set/erase-09.adoc[`erase`] 
| `erase` overloads
| xref:absl/linked_hash_set/extract-0ca.adoc[`extract`] 
| `extract` overloads
| xref:absl/linked_hash_set/find-0b.adoc[`find`] 
| Finds the element with the given key.
| xref:absl/linked_hash_set/front-06.adoc[`front`] 
| `front` overloads
| xref:absl/linked_hash_set/get_allocator.adoc[`get_allocator`] 
| Returns the allocator.
| xref:absl/linked_hash_set/hash_function.adoc[`hash_function`] 
| Returns the hash functor.
| xref:absl/linked_hash_set/insert-03e.adoc[`insert`] 
| `insert` overloads
| xref:absl/linked_hash_set/key_eq.adoc[`key_eq`] 
| Returns the key equality functor.
| xref:absl/linked_hash_set/load_factor.adoc[`load_factor`] 
| Returns the current load factor of the underlying hash set.
| xref:absl/linked_hash_set/max_size.adoc[`max_size`] 
| Returns the maximum number of elements the set can hold.
| xref:absl/linked_hash_set/merge-03.adoc[`merge`] 
| Merges the elements of another set into this one.
| xref:absl/linked_hash_set/pop_back.adoc[`pop_back`] 
| Removes the last element from the set.
| xref:absl/linked_hash_set/pop_front.adoc[`pop_front`] 
| Removes the first element from the set.
| xref:absl/linked_hash_set/rbegin-0a.adoc[`rbegin`] 
| `rbegin` overloads
| xref:absl/linked_hash_set/rehash.adoc[`rehash`] 
| Rehashes the underlying hash set to hold at least `n` buckets.
| xref:absl/linked_hash_set/rend-01.adoc[`rend`] 
| `rend` overloads
| xref:absl/linked_hash_set/reserve.adoc[`reserve`] 
| Reserves space for at least `n` elements.
| xref:absl/linked_hash_set/size.adoc[`size`] 
| Returns the number of elements in the set.
| xref:absl/linked_hash_set/swap.adoc[`swap`] 
| Swaps the contents of this set with another.
|===


== Friends

[cols="1,4"]
|===
| Name| Description
| `xref:absl/operator_not_eq-0563.adoc[absl::operator!=]`
| Returns whether two sets contain different elements.
| `xref:absl/operator_eq-08e.adoc[absl::operator==]`
| Returns whether two sets contain the same elements.
|===


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