(1) | ||
unordered_set() : unordered_set(size_type(/* implementation-defined */)) {} | (since C++11) (until C++20) | |
unordered_set(); | (since C++20) | |
explicit unordered_set( size_type bucket_count, const Hash& hash = Hash(), const key_equal& equal = key_equal(), const Allocator& alloc = Allocator() ); | (2) | (since C++11) |
unordered_set( size_type bucket_count, const Allocator& alloc ) : unordered_set(bucket_count, Hash(), key_equal(), alloc) {} | (3) | (since C++14) |
unordered_set( size_type bucket_count, const Hash& hash, const Allocator& alloc ) : unordered_set(bucket_count, hash, key_equal(), alloc) {} | (4) | (since C++14) |
explicit unordered_set( const Allocator& alloc ); | (5) | (since C++11) |
template< class InputIt > unordered_set( InputIt first, InputIt last, size_type bucket_count = /* implementation-defined */, const Hash& hash = Hash(), const key_equal& equal = key_equal(), const Allocator& alloc = Allocator() ); | (6) | (since C++11) |
template< class InputIt > unordered_set( InputIt first, InputIt last, size_type bucket_count, const Allocator& alloc ) : unordered_set(first, last, bucket_count, Hash(), key_equal(), alloc) {} | (7) | (since C++14) |
template< class InputIt > unordered_set( InputIt first, InputIt last, size_type bucket_count, const Hash& hash, const Allocator& alloc ) : unordered_set(first, last, bucket_count, hash, key_equal(), alloc) {} | (8) | (since C++14) |
unordered_set( const unordered_set& other ); | (9) | (since C++11) |
unordered_set( const unordered_set& other, const Allocator& alloc ); | (10) | (since C++11) |
unordered_set( unordered_set&& other ); | (11) | (since C++11) |
unordered_set( unordered_set&& other, const Allocator& alloc ); | (12) | (since C++11) |
unordered_set( std::initializer_list<value_type> init, size_type bucket_count = /* implementation-defined */, const Hash& hash = Hash(), const key_equal& equal = key_equal(), const Allocator& alloc = Allocator() ); | (13) | (since C++11) |
unordered_set( std::initializer_list<value_type> init, size_type bucket_count, const Allocator& alloc ) : unordered_set(init, bucket_count, Hash(), key_equal(), alloc) {} | (14) | (since C++14) |
unordered_set( std::initializer_list<value_type> init, size_type bucket_count, const Hash& hash, const Allocator& alloc ) : unordered_set(init, bucket_count, hash, key_equal(), alloc) {} | (15) | (since C++14) |
template< container-compatible-range<value_type> R > unordered_set( std::from_range_t, R&& rg, size_type bucket_count = /* see description */, const Hash& hash = Hash(), const key_equal& equal = key_equal(), const Allocator& alloc = Allocator() ); | (16) | (since C++23) |
template< container-compatible-range<value_type> R > unordered_set( std::from_range_t, R&& rg, size_type bucket_count, const Allocator& alloc ) : unordered_set(std::from_range, std::forward<R>(rg), bucket_count, Hash(), key_equal(), alloc) {} | (17) | (since C++23) |
template< container-compatible-range<value_type> R > unordered_set( std::from_range_t, R&& rg, size_type bucket_count, const Hash& hash, const Alloc& alloc ) : unordered_set(std::from_range, std::forward<R>(rg), bucket_count, hash, key_equal(), alloc) {} | (18) | (since C++23) |
Constructs new container from a variety of data sources. Optionally uses user supplied bucket_count
as a minimal number of buckets to create, hash
as the hash function, equal
as the function to compare keys and alloc
as the allocator.
max_load_factor()
to 1.0
. For the default constructor, the number of buckets is implementation-defined.[
first
,
last
)
. Sets max_load_factor()
to 1.0
. If multiple elements in the range have keys that compare equivalent, it is unspecified which element is inserted (pending LWG2844).other
, copies the load factor, the predicate, and the hash function as well. If alloc
is not provided, allocator is obtained by calling std::allocator_traits<allocator_type>::select_on_container_copy_construction(other.get_allocator())
. The template parameter | (since C++23) |
other
using move semantics. If alloc
is not provided, allocator is obtained by move-construction from the allocator belonging to other
. The template parameter | (since C++23) |
init
, same as unordered_set(init.begin(), init.end())
.rg
. If multiple elements in the range have keys that compare equivalent, it is unspecified which element is inserted (pending LWG2844).alloc | - | allocator to use for all memory allocations of this container |
bucket_count | - | minimal number of buckets to use on initialization. If it is not specified, implementation-defined default value is used |
hash | - | hash function to use |
equal | - | comparison function to use for all key comparisons of this container |
first, last | - | the range [ first , last ) to copy the elements from |
rg | - | a container compatible range, that is, an input_range whose elements are convertible to value_type |
other | - | another container to be used as source to initialize the elements of the container with |
init | - | initializer list to initialize the elements of the container with |
Type requirements | ||
-InputIt must meet the requirements of LegacyInputIterator. |
std::distance(first, last)
), worst case quadratic, i.e. O(N2)other
alloc
is given and alloc != other.get_allocator()
, then linear.std::size(init)
), worst case O(N2)ranges::distance(rg)
), worst case O(N2)Calls to Allocator::allocate
may throw.
other
remain valid, but refer to elements that are now in *this
. The current standard makes this guarantee via the blanket statement in [container.rev.reqmts]/17, and a more direct guarantee is under consideration via LWG 2321. Although not formally required until C++23, some implementations has already put the template parameter Allocator
into non-deduced contexts in earlier modes.
Feature-test macro | Value | Std | Comment |
---|---|---|---|
__cpp_lib_containers_ranges | 202202L | (C++23) | Ranges-aware construction and insertion; overloads (16-18) |
The following behavior-changing defect reports were applied retroactively to previously published C++ standards.
DR | Applied to | Behavior as published | Correct behavior |
---|---|---|---|
LWG 2193 | C++11 | the default constructor (1) was explicit | made non-explicit |
(C++11) | assigns values to the container (public member function) |
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