23 Containers library [containers]

23.4 Associative containers [associative]

23.4.7 Class template multiset [multiset]

23.4.7.1 Class template multiset overview [multiset.overview]

1

A multiset is an associative container that supports equivalent keys (possibly contains multiple copies of the same key value) and provides for fast retrieval of the keys themselves. The multiset class supports bidirectional iterators.

2

A multiset satisfies all of the requirements of a container, of a reversible container ([container.requirements]), of an associative container ([associative.reqmts]), and of an allocator-aware container (Table [tab:containers.allocatoraware]). multiset also provides most operations described in ([associative.reqmts]) for duplicate keys. This means that a multiset supports the a_eq operations in ([associative.reqmts]) but not the a_uniq operations. For a multiset<Key> both the key_type and value_type are Key. Descriptions are provided here only for operations on multiset that are not described in one of these tables and for operations where there is additional semantic information.

namespace std {
  template <class Key, class Compare = less<Key>,
            class Allocator = allocator<Key> >
  class multiset {
  public:
    // types:
    typedef Key                                                     key_type;
    typedef Key                                                     value_type;
    typedef Compare                                                 key_compare;
    typedef Compare                                                 value_compare;
    typedef Allocator                                               allocator_type;
    typedef value_type&                                             reference;
    typedef const value_type&                                       const_reference;
    typedef implementation-defined                iterator;       // see [container.requirements]
    typedef implementation-defined                const_iterator; // see [container.requirements]
    typedef implementation-defined                size_type;      // see [container.requirements]
    typedef implementation-defined                difference_type;// see [container.requirements]
    typedef typename allocator_traits<Allocator>::pointer           pointer;
    typedef typename allocator_traits<Allocator>::const_pointer     const_pointer;
    typedef std::reverse_iterator<iterator>       reverse_iterator;
    typedef std::reverse_iterator<const_iterator> const_reverse_iterator;

    // construct/copy/destroy:
    explicit multiset(const Compare& comp = Compare(),
                      const Allocator& = Allocator());
    template <class InputIterator>
      multiset(InputIterator first, InputIterator last,
               const Compare& comp = Compare(),
               const Allocator& = Allocator());
    multiset(const multiset<Key,Compare,Allocator>& x);
    multiset(multiset<Key,Compare,Allocator>&& x);
    explicit multiset(const Allocator&);
    multiset(const multiset&, const Allocator&);
    multiset(multiset&&, const Allocator&);
    multiset(initializer_list<value_type>,
      const Compare& = Compare(),
      const Allocator& = Allocator());
   ~multiset();
    multiset<Key,Compare,Allocator>&
        operator=(const multiset<Key,Compare,Allocator>& x);
    multiset<Key,Compare,Allocator>&
        operator=(multiset<Key,Compare,Allocator>&& x);
    multiset& 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;

    reverse_iterator       rbegin() noexcept;
    const_reverse_iterator rbegin() const noexcept;
    reverse_iterator       rend() noexcept;
    const_reverse_iterator rend() const noexcept;

    const_iterator         cbegin() const noexcept;
    const_iterator         cend() const noexcept;
    const_reverse_iterator crbegin() const noexcept;
    const_reverse_iterator crend() const noexcept;

    // capacity:
    bool          empty() const noexcept;
    size_type     size() const noexcept;
    size_type     max_size() 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& x);
    iterator insert(value_type&& x);
    iterator insert(const_iterator position, const value_type& x);
    iterator insert(const_iterator position, value_type&& x);
    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& x);
    iterator  erase(const_iterator first, const_iterator last);
    void swap(multiset<Key,Compare,Allocator>&);
    void clear() noexcept;

    // observers:
    key_compare   key_comp() const;
    value_compare value_comp() const;

    // set operations:
    iterator        find(const key_type& x);
    const_iterator  find(const key_type& x) const;

    size_type count(const key_type& x) const;

    iterator        lower_bound(const key_type& x);
    const_iterator  lower_bound(const key_type& x) const;

    iterator        upper_bound(const key_type& x);
    const_iterator  upper_bound(const key_type& x) const;

    pair<iterator,iterator>             equal_range(const key_type& x);
    pair<const_iterator,const_iterator> equal_range(const key_type& x) const;
  };

  template <class Key, class Compare, class Allocator>
    bool operator==(const multiset<Key,Compare,Allocator>& x,
                    const multiset<Key,Compare,Allocator>& y);
  template <class Key, class Compare, class Allocator>
    bool operator< (const multiset<Key,Compare,Allocator>& x,
                    const multiset<Key,Compare,Allocator>& y);
  template <class Key, class Compare, class Allocator>
    bool operator!=(const multiset<Key,Compare,Allocator>& x,
                    const multiset<Key,Compare,Allocator>& y);
  template <class Key, class Compare, class Allocator>
    bool operator> (const multiset<Key,Compare,Allocator>& x,
                    const multiset<Key,Compare,Allocator>& y);
  template <class Key, class Compare, class Allocator>
    bool operator>=(const multiset<Key,Compare,Allocator>& x,
                    const multiset<Key,Compare,Allocator>& y);
  template <class Key, class Compare, class Allocator>
    bool operator<=(const multiset<Key,Compare,Allocator>& x,
                    const multiset<Key,Compare,Allocator>& y);

  // specialized algorithms:
  template <class Key, class Compare, class Allocator>
    void swap(multiset<Key,Compare,Allocator>& x,
              multiset<Key,Compare,Allocator>& y);
}

23.4.7.2 multiset constructors [multiset.cons]

explicit multiset(const Compare& comp = Compare(), const Allocator& = Allocator());

1

Effects: Constructs an empty set using the specified comparison object and allocator.

2

Complexity: Constant.

template <class InputIterator> multiset(InputIterator first, last, const Compare& comp = Compare(), const Allocator& = Allocator());

3

Requires: If the iterator's dereference operator returns an lvalue or a const rvalue, then Key shall be CopyConstructible.

4

Effects: Constructs an empty multiset using the specified comparison object and allocator, and inserts elements from the range [first,last).

5

Complexity: Linear in N if the range [first,last) is already sorted using comp and otherwise N logN, where N is last - first.

23.4.7.3 multiset specialized algorithms [multiset.special]

template <class Key, class Compare, class Allocator> void swap(multiset<Key,Compare,Allocator>& x, multiset<Key,Compare,Allocator>& y);

1

Effects: 

x.swap(y);