std::unordered_multiset

std::unordered_multiset is an associative container that contains set of possibly non-unique objects of type Key. Search, insertion, and removal have average constant-time complexity.

# Declarations

template<
class Key,
class Hash = std::hash<Key>,
class KeyEqual = std::equal_to<Key>,
class Allocator = std::allocator<Key>
> class unordered_multiset;

(since C++11)

namespace pmr {
template<
class Key,
class Hash = std::hash<Key>,
class Pred = std::equal_to<Key>
> using unordered_multiset = std::unordered_multiset<Key, Hash, Pred,
std::pmr::polymorphic_allocator<Key>>;
}

(since C++17)

# Notes

The member types iterator and const_iterator may be aliases to the same type. This means defining a pair of function overloads using the two types as parameter types may violate the One Definition Rule. Since iterator is convertible to const_iterator, a single function with a const_iterator as parameter type will work instead.

# Defect reports

# See also

• unordered_set
• multiset
• flat_multiset