< cpp‎ | container
Defined in header <set>

    class Key,
    class Compare = std::less<Key>,
    class Allocator = std::allocator<Key>

> class set;
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 concept, 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.


[edit] Member types

Member type Definition
key_type Key [edit]
value_type Key [edit]
size_type Unsigned integer type (usually std::size_t) [edit]
difference_type Signed integer type (usually std::ptrdiff_t) [edit]
key_compare Compare [edit]
value_compare Compare [edit]
allocator_type Allocator [edit]
Allocator::reference (until C++11)
value_type& (since C++11)
Allocator::const_reference (until C++11)
const value_type& (since C++11)
Allocator::pointer (until C++11)
std::allocator_traits<Allocator>::pointer (since C++11)
Allocator::const_pointer (until C++11)
std::allocator_traits<Allocator>::const_pointer (since C++11)
iterator Constant BidirectionalIterator [edit]
const_iterator Constant BidirectionalIterator [edit]
reverse_iterator std::reverse_iterator<iterator> [edit]
const_reverse_iterator std::reverse_iterator<const_iterator> [edit]
node_type(since C++17) a specialization of node handle representing a container node [edit]
insert_return_type(since C++17) type describing the result of inserting a node_type, a specialization of
template <class Iterator, class NodeType> struct /*unspecified*/ {
    Iterator position;
    bool     inserted;
    NodeType node;
instantiated with template arguments iterator and node_type. [edit]

[edit] Member functions

constructs the set
(public member function) [edit]
destructs the set
(public member function) [edit]
assigns values to the container
(public member function) [edit]
returns the associated allocator
(public member function) [edit]
returns an iterator to the beginning
(public member function) [edit]
returns an iterator to the end
(public member function) [edit]
returns a reverse iterator to the beginning
(public member function) [edit]
returns a reverse iterator to the end
(public member function) [edit]
checks whether the container is empty
(public member function) [edit]
returns the number of elements
(public member function) [edit]
returns the maximum possible number of elements
(public member function) [edit]
clears the contents
(public member function) [edit]
inserts elements or nodes (since C++17)
(public member function) [edit]
constructs element in-place
(public member function) [edit]
constructs elements in-place using a hint
(public member function) [edit]
erases elements
(public member function) [edit]
swaps the contents
(public member function) [edit]
extracts nodes from the container
(public member function) [edit]
splices nodes from another container
(public member function) [edit]
returns the number of elements matching specific key
(public member function) [edit]
finds element with specific key
(public member function) [edit]
returns range of elements matching a specific key
(public member function) [edit]
returns an iterator to the first element not less than the given key
(public member function) [edit]
returns an iterator to the first element greater than the given key
(public member function) [edit]
returns the function that compares keys
(public member function) [edit]
returns the function that compares keys in objects of type value_type
(public member function) [edit]

[edit] Non-member functions

lexicographically compares the values in the set
(function template) [edit]
specializes the std::swap algorithm
(function template) [edit]

[edit] Deduction guides(since C++17)

[edit] Notes

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.

[edit] Defect Reports

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