std::set

template<
    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>>;
}

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 types

template <class Iter, class NodeType> struct /*unspecified*/ {
    Iter     position;
    bool     inserted;
    NodeType node;
};

Member functions

Non-member functions

Deduction guides(since C++17)

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.

Defect Reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.