Defined in header <set> | ||
---|---|---|
template< class Key, class Compare = std::less<Key>, class Allocator = std::allocator<Key> > class set; | (1) | |
namespace pmr { template <class Key, class Compare = std::less<Key>> using set = std::set<Key, Compare, std::pmr::polymorphic_allocator<Key>>; } | (2) | (since C++17) |
std::set
is an associative container that contains a sorted set of unique objects of type Key
. Sorting is done using the key comparison function Compare. Search, removal, and insertion operations have logarithmic complexity. Sets are usually implemented as red-black trees.
Everywhere the standard library uses the Compare requirements, uniqueness is determined by using the equivalence relation. In imprecise terms, two objects a
and b
are considered equivalent if neither compares less than the other: !comp(a, b) && !comp(b, a)
.
std::set
meets the requirements of Container, AllocatorAwareContainer, AssociativeContainer and ReversibleContainer.
Member type | Definition | ||||
---|---|---|---|---|---|
key_type | Key |
||||
value_type | Key |
||||
size_type | Unsigned integer type (usually std::size_t ) |
||||
difference_type | Signed integer type (usually std::ptrdiff_t ) |
||||
key_compare | Compare |
||||
value_compare | Compare |
||||
allocator_type | Allocator |
||||
reference |
|
||||
const_reference |
|
||||
pointer |
|
||||
const_pointer |
|
||||
iterator | Constant LegacyBidirectionalIterator | ||||
const_iterator | Constant LegacyBidirectionalIterator | ||||
reverse_iterator | std::reverse_iterator<iterator> |
||||
const_reverse_iterator | std::reverse_iterator<const_iterator> |
||||
node_type (since C++17) | a specialization of node handle representing a container node | ||||
insert_return_type (since C++17) | type describing the result of inserting a node_type , a specialization of template <class Iter, class NodeType> struct /*unspecified*/ { Iter position; bool inserted; NodeType node; }; iterator and node_type . |
constructs the set (public member function) |
|
destructs the set (public member function) |
|
assigns values to the container (public member function) |
|
returns the associated allocator (public member function) |
|
Iterators |
|
returns an iterator to the beginning (public member function) |
|
returns an iterator to the end (public member function) |
|
returns a reverse iterator to the beginning (public member function) |
|
returns a reverse iterator to the end (public member function) |
|
Capacity |
|
checks whether the container is empty (public member function) |
|
returns the number of elements (public member function) |
|
returns the maximum possible number of elements (public member function) |
|
Modifiers |
|
clears the contents (public member function) |
|
inserts elements or nodes (since C++17) (public member function) |
|
(C++11) | constructs element in-place (public member function) |
(C++11) | constructs elements in-place using a hint (public member function) |
erases elements (public member function) |
|
swaps the contents (public member function) |
|
(C++17) | extracts nodes from the container (public member function) |
(C++17) | splices nodes from another container (public member function) |
Lookup |
|
returns the number of elements matching specific key (public member function) |
|
finds element with specific key (public member function) |
|
(C++20) | checks if the container contains element with specific key (public member function) |
returns range of elements matching a specific key (public member function) |
|
returns an iterator to the first element not less than the given key (public member function) |
|
returns an iterator to the first element greater than the given key (public member function) |
|
Observers |
|
returns the function that compares keys (public member function) |
|
returns the function that compares keys in objects of type value_type (public member function) |
lexicographically compares the values in the set (function template) |
|
specializes the std::swap algorithm (function template) |
|
(C++20) | Erases all elements satisfying specific criteria (function template) |
The member types iterator
and const_iterator
may be aliases to the same type. Since iterator
is convertible to const_iterator
, const_iterator
should be used in function parameter lists to avoid violations of the One Definition Rule.
The following behavior-changing defect reports were applied retroactively to previously published C++ standards.
DR | Applied to | Behavior as published | Correct behavior |
---|---|---|---|
LWG 103 | C++98 | iterator allows modification of keys | iterator made constant |
© cppreference.com
Licensed under the Creative Commons Attribution-ShareAlike Unported License v3.0.
http://en.cppreference.com/w/cpp/container/set