std::unordered_map

Defined in header <unordered_map>
template<     class Key,     class T,     class Hash = std::hash<Key>,     class KeyEqual = std::equal_to<Key>,     class Allocator = std::allocator< std::pair<const Key, T> > > class unordered_map;		(since C++11)

Unordered map is an associative container that contains key-value pairs with unique keys. Search, insertion, and removal have average constant-time complexity.

std::unordered_map meets the requirements of Container, AllocatorAwareContainer, UnorderedAssociativeContainer.

Member functions

(constructor)	constructs the unordered_map (public member function)
(destructor)	destructs the unordered_map (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
at	access specified element with bounds checking (public member function)
operator[]	access specified element (public member function)
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)

Non-member functions

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