23 Containers library [containers]

An unordered_multiset is an unordered associative container that supports equivalent keys (an instance of unordered_multiset may contain multiple copies of the same key value) and in which each element's key is the element itself. The unordered_multiset class supports forward iterators.

An unordered_multiset satisfies all of the requirements of a container, of an unordered associative container, and of an allocator-aware container (Table [tab:containers.allocatoraware]). It provides the operations described in the preceding requirements table for equivalent keys; that is, an unordered_multiset supports the a_eq operations in that table, not the a_uniq operations. For an unordered_multiset<Key> the key type and the value type are both Key. The iterator and const_iterator types are both const iterator types. It is unspecified whether they are the same type.

This section only describes operations on unordered_multiset that are not described in one of the requirement tables, or for which there is additional semantic information.

namespace std {
  template <class Key,
            class Hash  = hash<Key>,
            class Pred  = std::equal_to<Key>,
            class Allocator = std::allocator<Key> >
  class unordered_multiset
  {
  public:
    // types
    typedef Key                                      key_type;
    typedef Key                                      value_type;
    typedef Hash                                     hasher;
    typedef Pred                                     key_equal;
    typedef Allocator                                allocator_type;
    typedef typename allocator_type::pointer         pointer;
    typedef typename allocator_type::const_pointer   const_pointer;
    typedef typename allocator_type::reference       reference;
    typedef typename allocator_type::const_reference const_reference;
    typedef implementation-defined                   size_type;
    typedef implementation-defined                   difference_type;

    typedef implementation-defined                   iterator;
    typedef implementation-defined                   const_iterator;
    typedef implementation-defined                   local_iterator;
    typedef implementation-defined                   const_local_iterator;

    // construct/destroy/copy
    explicit unordered_multiset(size_type n = see below,
                                const hasher& hf = hasher(),
                                const key_equal& eql = key_equal(),
                                const allocator_type& a = allocator_type());
    template <class InputIterator>
      unordered_multiset(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_multiset(const unordered_multiset&);
    unordered_multiset(unordered_multiset&&);
    explicit unordered_multiset(const Allocator&);
    unordered_multiset(const unordered_multiset&, const Allocator&);
    unordered_multiset(unordered_multiset&&, const Allocator&);
    unordered_multiset(initializer_list<value_type>,
      size_type = see below,
      const hasher& hf = hasher(),
      const key_equal& eql = key_equal(),
      const allocator_type& a = allocator_type());
    ~unordered_multiset();
    unordered_multiset& operator=(const unordered_multiset&);
    unordered_multiset operator=(unordered_multiset&&);
    unordered_multiset& operator=(initializer_list<value_type>);
    allocator_type get_allocator() const noexcept;

    // size and capacity
    bool empty() const noexcept;
    size_type size() const noexcept;
    size_type max_size() 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;

    // 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);
    iterator insert(const_iterator hint, const value_type& obj);
    iterator insert(const_iterator hint, value_type&& obj);
    template <class InputIterator> void insert(InputIterator first, InputIterator last);
    void insert(initializer_list<value_type>);

    iterator erase(const_iterator position);
    size_type erase(const key_type& k);
    iterator erase(const_iterator first, const_iterator last);
    void clear() noexcept;

    void swap(unordered_multiset&);

    // observers
    hasher hash_function() const;
    key_equal key_eq() const;

    // lookup
    iterator       find(const key_type& k);
    const_iterator find(const key_type& k) const;
    size_type count(const key_type& k) const;
    std::pair<iterator, iterator>             equal_range(const key_type& k);
    std::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 Key, class Hash, class Pred, class Alloc>
    void swap(unordered_multiset<Key, Hash, Pred, Alloc>& x,
              unordered_multiset<Key, Hash, Pred, Alloc>& y);
    template <class Key, class T, class Hash, class Pred, class Alloc>
      bool operator==(const unordered_multiset<Key, T, Hash, Pred, Alloc>& a,
                      const unordered_multiset<Key, T, Hash, Pred, Alloc>& b);
    template <class Key, class T, class Hash, class Pred, class Alloc>
      bool operator!=(const unordered_multiset<Key, T, Hash, Pred, Alloc>& a,
                      const unordered_multiset<Key, T, Hash, Pred, Alloc>& b);
}