An unordered_multimap is an unordered associative container that supports equivalent keys (an instance of unordered_multimap may contain multiple copies of each key value) and that associates values of another type mapped_type with the keys. The unordered_multimap class supports forward iterators.
An unordered_multimap satisfies all of the requirements of a container, of an unordered associative container, and of an allocator-aware container. It provides the operations described in the preceding requirements table for equivalent keys; that is, an unordered_multimap supports the a_eq operations in that table, not the a_uniq operations. For an unordered_multimap<Key, T> the key type is Key, the mapped type is T, and the value type is pair<const Key, T>.
This section only describes operations on unordered_multimap that are not described in one of the requirement tables, or for which there is additional semantic information.
namespace std {
template <class Key,
class T,
class Hash = hash<Key>,
class Pred = equal_to<Key>,
class Allocator = allocator<pair<const Key, T>>>
class unordered_multimap {
public:
// types:
using key_type = Key;
using mapped_type = T;
using value_type = pair<const Key, T>;
using hasher = Hash;
using key_equal = Pred;
using allocator_type = Allocator;
using pointer = typename allocator_traits<Allocator>::pointer;
using const_pointer = typename allocator_traits<Allocator>::const_pointer;
using reference = value_type&;
using const_reference = const value_type&;
using size_type = implementation-defined; // see [container.requirements]
using difference_type = implementation-defined; // see [container.requirements]
using iterator = implementation-defined; // see [container.requirements]
using const_iterator = implementation-defined; // see [container.requirements]
using local_iterator = implementation-defined; // see [container.requirements]
using const_local_iterator = implementation-defined; // see [container.requirements]
using node_type = unspecified;
// [unord.multimap.cnstr], construct/copy/destroy
unordered_multimap();
explicit unordered_multimap(size_type n,
const hasher& hf = hasher(),
const key_equal& eql = key_equal(),
const allocator_type& a = allocator_type());
template <class InputIterator>
unordered_multimap(InputIterator f, InputIterator l,
size_type n = see below,
const hasher& hf = hasher(),
const key_equal& eql = key_equal(),
const allocator_type& a = allocator_type());
unordered_multimap(const unordered_multimap&);
unordered_multimap(unordered_multimap&&);
explicit unordered_multimap(const Allocator&);
unordered_multimap(const unordered_multimap&, const Allocator&);
unordered_multimap(unordered_multimap&&, const Allocator&);
unordered_multimap(initializer_list<value_type> il,
size_type n = see below,
const hasher& hf = hasher(),
const key_equal& eql = key_equal(),
const allocator_type& a = allocator_type());
unordered_multimap(size_type n, const allocator_type& a)
: unordered_multimap(n, hasher(), key_equal(), a) { }
unordered_multimap(size_type n, const hasher& hf, const allocator_type& a)
: unordered_multimap(n, hf, key_equal(), a) { }
template <class InputIterator>
unordered_multimap(InputIterator f, InputIterator l, size_type n, const allocator_type& a)
: unordered_multimap(f, l, n, hasher(), key_equal(), a) { }
template <class InputIterator>
unordered_multimap(InputIterator f, InputIterator l, size_type n, const hasher& hf,
const allocator_type& a)
: unordered_multimap(f, l, n, hf, key_equal(), a) { }
unordered_multimap(initializer_list<value_type> il, size_type n, const allocator_type& a)
: unordered_multimap(il, n, hasher(), key_equal(), a) { }
unordered_multimap(initializer_list<value_type> il, size_type n, const hasher& hf,
const allocator_type& a)
: unordered_multimap(il, n, hf, key_equal(), a) { }
~unordered_multimap();
unordered_multimap& operator=(const unordered_multimap&);
unordered_multimap& operator=(unordered_multimap&&)
noexcept(allocator_traits<Allocator>::is_always_equal::value &&
is_nothrow_move_assignable_v<Hash> &&
is_nothrow_move_assignable_v<Pred>);
unordered_multimap& operator=(initializer_list<value_type>);
allocator_type get_allocator() const noexcept;
// iterators:
iterator begin() noexcept;
const_iterator begin() const noexcept;
iterator end() noexcept;
const_iterator end() const noexcept;
const_iterator cbegin() const noexcept;
const_iterator cend() const noexcept;
// capacity:
bool empty() const noexcept;
size_type size() const noexcept;
size_type max_size() const noexcept;
// [unord.multimap.modifiers], modifiers
template <class... Args> iterator emplace(Args&&... args);
template <class... Args> iterator emplace_hint(const_iterator position, Args&&... args);
iterator insert(const value_type& obj);
iterator insert(value_type&& obj);
template <class P> iterator insert(P&& obj);
iterator insert(const_iterator hint, const value_type& obj);
iterator insert(const_iterator hint, value_type&& obj);
template <class P> iterator insert(const_iterator hint, P&& obj);
template <class InputIterator> void insert(InputIterator first, InputIterator last);
void insert(initializer_list<value_type>);
node_type extract(const_iterator position);
node_type extract(const key_type& x);
iterator insert(node_type&& nh);
iterator insert(const_iterator hint, node_type&& nh);
iterator erase(iterator position);
iterator erase(const_iterator position);
size_type erase(const key_type& k);
iterator erase(const_iterator first, const_iterator last);
void swap(unordered_multimap&)
noexcept(allocator_traits<Allocator>::is_always_equal::value &&
is_nothrow_swappable_v<Hash> &&
is_nothrow_swappable_v<Pred>);
void clear() noexcept;
template<class H2, class P2>
void merge(unordered_multimap<Key, T, H2, P2, Allocator>& source);
template<class H2, class P2>
void merge(unordered_multimap<Key, T, H2, P2, Allocator>&& source);
template<class H2, class P2>
void merge(unordered_map<Key, T, H2, P2, Allocator>& source);
template<class H2, class P2>
void merge(unordered_map<Key, T, H2, P2, Allocator>&& source);
// observers:
hasher hash_function() const;
key_equal key_eq() const;
// map operations:
iterator find(const key_type& k);
const_iterator find(const key_type& k) const;
size_type count(const key_type& k) const;
pair<iterator, iterator> equal_range(const key_type& k);
pair<const_iterator, const_iterator> equal_range(const key_type& k) const;
// bucket interface:
size_type bucket_count() const noexcept;
size_type max_bucket_count() const noexcept;
size_type bucket_size(size_type n) const;
size_type bucket(const key_type& k) const;
local_iterator begin(size_type n);
const_local_iterator begin(size_type n) const;
local_iterator end(size_type n);
const_local_iterator end(size_type n) const;
const_local_iterator cbegin(size_type n) const;
const_local_iterator cend(size_type n) const;
// hash policy
float load_factor() const noexcept;
float max_load_factor() const noexcept;
void max_load_factor(float z);
void rehash(size_type n);
void reserve(size_type n);
};
template<class InputIterator,
class Hash = hash<iter_key_t<InputIterator>>,
class Pred = equal_to<iter_key_t<InputIterator>>,
class Allocator = allocator<iter_to_alloc_t<InputIterator>>>
unordered_multimap(InputIterator, InputIterator,
typename see below::size_type = see below,
Hash = Hash(), Pred = Pred(), Allocator = Allocator())
-> unordered_multimap<iter_key_t<InputIterator>, iter_value_t<InputIterator>, Hash, Pred,
Allocator>;
template<class Key, class T, class Hash = hash<Key>,
class Pred = equal_to<Key>, class Allocator = allocator<pair<const Key, T>>>
unordered_multimap(initializer_list<pair<const Key, T>>,
typename see below::size_type = see below,
Hash = Hash(), Pred = Pred(), Allocator = Allocator())
-> unordered_multimap<Key, T, Hash, Pred, Allocator>;
template<class InputIterator, class Allocator>
unordered_multimap(InputIterator, InputIterator, typename see below::size_type, Allocator)
-> unordered_multimap<iter_key_t<InputIterator>, iter_val_t<InputIterator>,
hash<iter_key_t<InputIterator>>,
equal_to<iter_key_t<InputIterator>>, Allocator>;
template<class InputIterator, class Allocator>
unordered_multimap(InputIterator, InputIterator, Allocator)
-> unordered_multimap<iter_key_t<InputIterator>, iter_val_t<InputIterator>,
hash<iter_key_t<InputIterator>>,
equal_to<iter_key_t<InputIterator>>, Allocator>;
template<class InputIterator, class Hash, class Allocator>
unordered_multimap(InputIterator, InputIterator, typename see below::size_type, Hash,
Allocator)
-> unordered_multimap<iter_key_t<InputIterator>, iter_val_t<InputIterator>, Hash,
equal_to<iter_key_t<InputIterator>>, Allocator>;
template<class Key, class T, typename Allocator>
unordered_multimap(initializer_list<pair<const Key, T>>, typename see below::size_type,
Allocator)
-> unordered_multimap<Key, T, hash<Key>, equal_to<Key>, Allocator>;
template<class Key, class T, typename Allocator>
unordered_multimap(initializer_list<pair<const Key, T>>, Allocator)
-> unordered_multimap<Key, T, hash<Key>, equal_to<Key>, Allocator>;
template<class Key, class T, class Hash, class Allocator>
unordered_multimap(initializer_list<pair<const Key, T>>, typename see below::size_type,
Hash, Allocator)
-> unordered_multimap<Key, T, Hash, equal_to<Key>, Allocator>;
template <class Key, class T, class Hash, class Pred, class Alloc>
bool operator==(const unordered_multimap<Key, T, Hash, Pred, Alloc>& a,
const unordered_multimap<Key, T, Hash, Pred, Alloc>& b);
template <class Key, class T, class Hash, class Pred, class Alloc>
bool operator!=(const unordered_multimap<Key, T, Hash, Pred, Alloc>& a,
const unordered_multimap<Key, T, Hash, Pred, Alloc>& b);
// [unord.multimap.swap], swap
template <class Key, class T, class Hash, class Pred, class Alloc>
void swap(unordered_multimap<Key, T, Hash, Pred, Alloc>& x,
unordered_multimap<Key, T, Hash, Pred, Alloc>& y)
noexcept(noexcept(x.swap(y)));
}unordered_multimap() : unordered_multimap(size_type(see below)) { }
explicit unordered_multimap(size_type n,
const hasher& hf = hasher(),
const key_equal& eql = key_equal(),
const allocator_type& a = allocator_type());
template <class InputIterator>
unordered_multimap(InputIterator f, InputIterator l,
size_type n = see below,
const hasher& hf = hasher(),
const key_equal& eql = key_equal(),
const allocator_type& a = allocator_type());
unordered_multimap(initializer_list<value_type> il,
size_type n = see below,
const hasher& hf = hasher(),
const key_equal& eql = key_equal(),
const allocator_type& a = allocator_type());
Effects: Constructs an empty unordered_multimap using the specified hash function, key equality predicate, and allocator, and using at least n buckets. If n is not provided, the number of buckets is implementation-defined. Then inserts elements from the range [f, l) for the first form, or from the range [il.begin(), il.end()) for the second form. max_load_factor() returns 1.0.
template <class P>
iterator insert(P&& obj);
Remarks: This signature shall not participate in overload resolution unless is_constructible_v<value_type, P&&> is true.
template <class P>
iterator insert(const_iterator hint, P&& obj);
template <class Key, class T, class Hash, class Pred, class Alloc>
void swap(unordered_multimap<Key, T, Hash, Pred, Alloc>& x,
unordered_multimap<Key, T, Hash, Pred, Alloc>& y)
noexcept(noexcept(x.swap(y)));