std::unordered_multimap

std::unordered_multimap is an unordered associative container that supports equivalent keys (an unordered_multimap may contain multiple copies of each key value) and that associates values of another type with the keys. The unordered_multimap class supports forward iterators. Search, insertion, and removal have average constant-time complexity.

# Declarations

template<
class Key,
class T,
class Hash = std::hash<Key>,
class KeyEqual = std::equal_to<Key>,
class Allocator = std::allocator<std::pair<const Key, T>>
> class unordered_multimap;

(since C++11)

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

(since C++17)

# Notes

Feature-test macro Value Std Feature __cpp_lib_containers_ranges 202202L (C++23) Ranges construction and insertion for containers

# Defect reports

# See also

• unordered_map
• multimap
• flat_multimap