std::unordered_set

From Cppreference

C++ Standard Library
Language Utilities library Strings library Containers library Algorithms library Iterators library Numerics library Input/output library Localizations library Regular expressions library (C++11) Atomic operations library (C++11) Thread support library (C++11)
Containers library
array (C++11) vector deque forward_list (C++11) list set multiset map multimap unordered_set (C++11) unordered_multiset (C++11) unordered_map (C++11) unordered_multimap (C++11) stack queue priority_queue
std::unordered_set
Member functions unordered_set::unordered_set unordered_set::~unordered_set unordered_set::operator= unordered_set::get_allocator Iterators unordered_set::begin unordered_set::cbegin unordered_set::end unordered_set::cend Capacity unordered_set::erase unordered_set::size unordered_set::max_size Modifiers unordered_set::clear unordered_set::insert unordered_set::emplace unordered_set::emplace_hint unordered_set::erase unordered_set::swap Lookup unordered_set::count unordered_set::find unordered_set::equal_range Bucket interface unordered_set::begin(int) unordered_set::end(int) unordered_set::bucket_count unordered_set::max_bucket_count unordered_set::bucket_size unordered_set::bucket Hash policy unordered_set::load_factor unordered_set::max_load_factor unordered_set::rehash unordered_set::reserve Observers unordered_set::hash_function unordered_set::key_eq

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_set;		(C++11 feature)

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

Contents 1 Member types 2 Member functions 2.1 Iterators 2.2 Capacity 2.3 Modifiers 2.4 Lookup 2.5 Bucket interface 2.6 Hash policy 2.7 Observers 3 Non-member functions

[edit] Member types

Member type	Definition
key_type	Key
value_type	Key
size_type	Unsigned integral type (usually size_t)
difference_type	Signed integer type (usually ptrdiff_t)
hasher	Hash
key_equal	KeyEqual
allocator_type	Allocator
reference	value_type&
const_reference	const value_type&
pointer	std::allocator_traits<Allocator>::pointer
const_pointer	std::allocator_traits<Allocator>::const_pointer
iterator	Forward iterator
const_iterator	Constant forward iterator
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
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] Member functions

(constructor)	constructs the unordered_set (public member function)
(destructor)	destructs the unordered_set (public member function)
operator=	assigns values to the container (public member function)
get_allocator	returns the associated allocator (public member function)
Iterators
begin cbegin	returns an iterator to the beginning (public member function)
end cend	returns an iterator to the end (public member function)
Capacity
empty	checks whether the container is empty (public member function)
size	returns the number of elements (public member function)
max_size	returns the maximum possible number of elements (public member function)
Modifiers
clear	clears the contents (public member function)
insert	inserts elements (public member function)
emplace	constructs element in-place (public member function)
emplace_hint	constructs elements in-place using a hint (public member function)
erase	erases elements (public member function)
swap	swaps the contents (public member function)
Lookup
count	returns the number of elements matching specific key (public member function)
find	finds element with specific key (public member function)
equal_range	returns range of elements matching a specific key (public member function)
Bucket interface
begin(int) cbegin(int)	returns an iterator to the beginning of the specified bucket (public member function)
end(int) cend(int)	returns an iterator to the end of the specified bucket (public member function)
bucket_count	returns the number of buckets (public member function)
max_bucket_count	returns the maximum number of buckets (public member function)
bucket_size	returns the number of elements in specific bucket (public member function)
bucket	returns the bucket for specific key (public member function)
Hash policy
load_factor	returns average number of elements per bucket (public member function)
max_load_factor	manages maximum average number of elements per bucket (public member function)
rehash	reserves at least the specified number of buckets. This regenerates the hash table. (public member function)
reserve	reserves space for at least the specified number of elements. This regenerates the hash table. (public member function)
Observers
hash_function	returns function used to hash the keys (public member function)
key_eq	returns the function used to compare keys for equality (public member function)

[edit] Non-member functions

operator= operator!=	compares the values in the container (function)
std::swap(std::unordered_set)	specializes the std::swap() algorithm (function template)