标准库标头 <flat_map> (C++23) - cppreference.com

此标头是容器库的一部分。

包含
<compare> (C++20)	三路比较运算符支持[编辑]
<initializer_list> (C++11)	std::initializer_list 类模板[编辑]
类
flat_map (C++23)	适配两个容器以提供按唯一键排序的键值对集合 (类模板) [编辑]
flat_multimap (C++23)	适配两个容器以提供按键排序的键值对集合 (类模板) [编辑]
std::uses_allocator<std::flat_map> (C++11)	特化 std::uses_allocator 类型特征 (类模板特化) [编辑]
std::uses_allocator<std::flat_multimap> (C++11)	特化 std::uses_allocator 类型特征 (类模板特化) [编辑]
函数
erase_if(std::flat_map) (C++23)	擦除所有满足特定判别标准的元素 (函数模板) [编辑]
erase_if(std::flat_multimap) (C++23)	擦除所有满足特定判别标准的元素 (函数模板) [编辑]
标签
sorted_uniquesorted_unique_t (C++23)	指出范围的元素有序且唯一 (标签) [编辑]
sorted_equivalentsorted_equivalent_t (C++23)	指出范围的元素有序（不要求唯一） (标签) [编辑]

概要

#include <compare>
#include <initializer_list>

namespace std {
  // 类模板 flat_map
  template<class Key,
           class T,
           class Compare = less<Key>,
           class KeyContainer = vector<Key>,
           class MappedContainer = vector<T>>
  class flat_map;

  struct sorted_unique_t
  {
    explicit sorted_unique_t() = default;
  };
  inline constexpr sorted_unique_t sorted_unique{};

  template<class Key,
           class T,
           class Compare,
           class KeyContainer,
           class MappedContainer,
           class Allocator>
  struct uses_allocator<flat_map<Key, T, Compare, KeyContainer, MappedContainer>,
                        Allocator>;

  // flat_map 的擦除
  template<class Key,
           class T,
           class Compare,
           class KeyContainer,
           class MappedContainer,
           class Predicate>
  constexpr typename flat_map<Key, T, Compare, KeyContainer, MappedContainer>::size_type
  erase_if(flat_map<Key, T, Compare, KeyContainer, MappedContainer>& c, Predicate pred);

  // 类模板 flat_multimap
  template<class Key,
           class T,
           class Compare = less<Key>,
           class KeyContainer = vector<Key>,
           class MappedContainer = vector<T>>
  class flat_multimap;

  struct sorted_equivalent_t
  {
    explicit sorted_equivalent_t() = default;
  };
  inline constexpr sorted_equivalent_t sorted_equivalent{};

  template<class Key,
           class T,
           class Compare,
           class KeyContainer,
           class MappedContainer,
           class Allocator>
  struct uses_allocator<flat_multimap<Key, T, Compare, KeyContainer, MappedContainer>,
                        Allocator>;

  // flat_multimap 的擦除
  template<class Key,
           class T,
           class Compare,
           class KeyContainer,
           class MappedContainer,
           class Predicate>
  constexpr
    typename flat_multimap<Key, T, Compare, KeyContainer, MappedContainer>::size_type
    erase_if(flat_multimap<Key, T, Compare, KeyContainer, MappedContainer>& c,
             Predicate pred);
}

类模板 `std::flat_map`

namespace std {
  template<class Key,
           class T,
           class Compare = less<Key>,
           class KeyContainer = vector<Key>,
           class MappedContainer = vector<T>>
  class flat_map
  {
  public:
    // 类型
    using key_type = Key;
    using mapped_type = T;
    using value_type = pair<key_type, mapped_type>;
    using key_compare = Compare;
    using reference = pair<const key_type&, mapped_type&>;
    using const_reference = pair<const key_type&, const mapped_type&>;
    using size_type = size_t;
    using difference_type = ptrdiff_t;
    using iterator = /* 由实现定义 */;
    using const_iterator = /* 由实现定义 */;
    using reverse_iterator = std::reverse_iterator<iterator>;
    using const_reverse_iterator = std::reverse_iterator<const_iterator>;
    using key_container_type = KeyContainer;
    using mapped_container_type = MappedContainer;

    class value_compare
    {
    private:
      key_compare /*comp*/; // 仅用于阐释
      constexpr value_compare(key_compare c)
        : /*comp*/(c)
      {
      }                     // 仅用于阐释

    public:
      constexpr bool operator()(const_reference x, const_reference y) const
      {
        return /*comp*/(x.first, y.first);
      }
    };

    struct containers
    {
      key_container_type keys;
      mapped_container_type values;
    };

    // 构造函数
    constexpr flat_map()
      : flat_map(key_compare())
    {
    }

    constexpr flat_map(const flat_map&);
    constexpr flat_map(flat_map&&);
    constexpr flat_map& operator=(const flat_map&);
    constexpr flat_map& operator=(flat_map&&);

    constexpr explicit flat_map(const key_compare& comp)
      : /*c*/()
      , /*compare*/(comp)
    {
    }

    constexpr flat_map(key_container_type key_cont,
                       mapped_container_type mapped_cont,
                       const key_compare& comp = key_compare());

    constexpr flat_map(sorted_unique_t,
                       key_container_type key_cont,
                       mapped_container_type mapped_cont,
                       const key_compare& comp = key_compare());

    template<class InputIter>
    constexpr flat_map(InputIter first,
                       InputIter last,
                       const key_compare& comp = key_compare())
      : /*c*/()
      , /*compare*/(comp)
    {
      insert(first, last);
    }

    template<class InputIter>
    constexpr flat_map(sorted_unique_t,
                       InputIter first,
                       InputIter last,
                       const key_compare& comp = key_compare())
      : /*c*/()
      , /*compare*/(comp)
    {
      insert(sorted_unique, first, last);
    }

    template<container-compatible-range<value_type> R>
    constexpr flat_map(from_range_t, R&& rg)
      : flat_map(from_range, std::forward<R>(rg), key_compare())
    {
    }
    template<container-compatible-range<value_type> R>
    constexpr flat_map(from_range_t, R&& rg, const key_compare& comp)
      : flat_map(comp)
    {
      insert_range(std::forward<R>(rg));
    }

    constexpr flat_map(initializer_list<value_type> il,
                       const key_compare& comp = key_compare())
      : flat_map(il.begin(), il.end(), comp)
    {
    }

    constexpr flat_map(sorted_unique_t,
                       initializer_list<value_type> il,
                       const key_compare& comp = key_compare())
      : flat_map(sorted_unique, il.begin(), il.end(), comp)
    {
    }

    // 带分配器的构造函数

    template<class Alloc> constexpr explicit flat_map(const Alloc& a);
    template<class Alloc> constexpr flat_map(const key_compare& comp, const Alloc& a);
    template<class Alloc>
    constexpr flat_map(const key_container_type& key_cont,
                       const mapped_container_type& mapped_cont,
                       const Alloc& a);
    template<class Alloc>
    constexpr flat_map(const key_container_type& key_cont,
                       const mapped_container_type& mapped_cont,
                       const key_compare& comp,
                       const Alloc& a);
    template<class Alloc>
    constexpr flat_map(sorted_unique_t,
                       const key_container_type& key_cont,
                       const mapped_container_type& mapped_cont,
                       const Alloc& a);
    template<class Alloc>
    constexpr flat_map(sorted_unique_t,
                       const key_container_type& key_cont,
                       const mapped_container_type& mapped_cont,
                       const key_compare& comp,
                       const Alloc& a);
    template<class Alloc> constexpr flat_map(const flat_map&, const Alloc& a);
    template<class Alloc> constexpr flat_map(flat_map&&, const Alloc& a);
    template<class InputIter, class Alloc>
    constexpr flat_map(InputIter first, InputIter last, const Alloc& a);
    template<class InputIter, class Alloc>
    constexpr flat_map(InputIter first,
                       InputIter last,
                       const key_compare& comp,
                       const Alloc& a);
    template<class InputIter, class Alloc>
    constexpr flat_map(sorted_unique_t, InputIter first, InputIter last, const Alloc& a);
    template<class InputIter, class Alloc>
    constexpr flat_map(sorted_unique_t,
                       InputIter first,
                       InputIter last,
                       const key_compare& comp,
                       const Alloc& a);
    template<container-compatible-range<value_type> R, class Alloc>
    constexpr flat_map(from_range_t, R&& rg, const Alloc& a);
    template<container-compatible-range<value_type> R, class Alloc>
    constexpr flat_map(from_range_t, R&& rg, const key_compare& comp, const Alloc& a);
    template<class Alloc>
    constexpr flat_map(initializer_list<value_type> il, const Alloc& a);
    template<class Alloc>
    constexpr flat_map(initializer_list<value_type> il,
                       const key_compare& comp,
                       const Alloc& a);
    template<class Alloc>
    constexpr flat_map(sorted_unique_t, initializer_list<value_type> il, const Alloc& a);
    template<class Alloc>
    constexpr flat_map(sorted_unique_t,
                       initializer_list<value_type> il,
                       const key_compare& comp,
                       const Alloc& a);

    constexpr flat_map& operator=(initializer_list<value_type>);

    // 迭代器
    constexpr iterator begin() noexcept;
    constexpr const_iterator begin() const noexcept;
    constexpr iterator end() noexcept;
    constexpr const_iterator end() const noexcept;

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

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

    // 容量
    constexpr bool empty() const noexcept;
    constexpr size_type size() const noexcept;
    constexpr size_type max_size() const noexcept;

    // 元素访问
    constexpr mapped_type& operator[](const key_type& x);
    constexpr mapped_type& operator[](key_type&& x);
    template<class K> constexpr mapped_type& operator[](K&& x);
    constexpr mapped_type& at(const key_type& x);
    constexpr const mapped_type& at(const key_type& x) const;
    template<class K> constexpr mapped_type& at(const K& x);
    template<class K> constexpr const mapped_type& at(const K& x) const;

    // 修改器
    template<class... Args> constexpr pair<iterator, bool> emplace(Args&&... args);
    template<class... Args>
    constexpr iterator emplace_hint(const_iterator position, Args&&... args);

    constexpr pair<iterator, bool> insert(const value_type& x) { return emplace(x); }
    constexpr pair<iterator, bool> insert(value_type&& x)
    {
      return emplace(std::move(x));
    }
    constexpr iterator insert(const_iterator position, const value_type& x)
    {
      return emplace_hint(position, x);
    }
    constexpr iterator insert(const_iterator position, value_type&& x)
    {
      return emplace_hint(position, std::move(x));
    }

    template<class P> constexpr pair<iterator, bool> insert(P&& x);
    template<class P> constexpr iterator insert(const_iterator position, P&&);
    template<class InputIter> constexpr void insert(InputIter first, InputIter last);
    template<class InputIter>
    constexpr void insert(sorted_unique_t, InputIter first, InputIter last);
    template<container-compatible-range<value_type> R>
    constexpr void insert_range(R&& rg);
    template<container-compatible-range<value_type> R>
    constexpr void insert_range(sorted_unique_t, R&& rg);

    constexpr void insert(initializer_list<value_type> il)
    {
      insert(il.begin(), il.end());
    }
    constexpr void insert(sorted_unique_t, initializer_list<value_type> il)
    {
      insert(sorted_unique, il.begin(), il.end());
    }

    constexpr containers extract() &&;
    constexpr void replace(key_container_type&& key_cont,
                           mapped_container_type&& mapped_cont);

    template<class... Args>
    constexpr pair<iterator, bool> try_emplace(const key_type& k, Args&&... args);
    template<class... Args>
    constexpr pair<iterator, bool> try_emplace(key_type&& k, Args&&... args);
    template<class K, class... Args>
    constexpr pair<iterator, bool> try_emplace(K&& k, Args&&... args);
    template<class... Args>
    constexpr iterator try_emplace(const_iterator hint,
                                   const key_type& k,
                                   Args&&... args);
    template<class... Args>
    constexpr iterator try_emplace(const_iterator hint, key_type&& k, Args&&... args);
    template<class K, class... Args>
    constexpr iterator try_emplace(const_iterator hint, K&& k, Args&&... args);
    template<class M>
    constexpr pair<iterator, bool> insert_or_assign(const key_type& k, M&& obj);
    template<class M>
    constexpr pair<iterator, bool> insert_or_assign(key_type&& k, M&& obj);
    template<class K, class M>
    constexpr pair<iterator, bool> insert_or_assign(K&& k, M&& obj);
    template<class M>
    constexpr iterator insert_or_assign(const_iterator hint, const key_type& k, M&& obj);
    template<class M>
    constexpr iterator insert_or_assign(const_iterator hint, key_type&& k, M&& obj);
    template<class K, class M>
    constexpr iterator insert_or_assign(const_iterator hint, K&& k, M&& obj);

    constexpr iterator erase(iterator position);
    constexpr iterator erase(const_iterator position);
    constexpr size_type erase(const key_type& x);
    template<class K> constexpr size_type erase(K&& x);
    constexpr iterator erase(const_iterator first, const_iterator last);

    constexpr void swap(flat_map& y) noexcept(/* 见描述 */);
    constexpr void clear() noexcept;

    // 观察器
    constexpr key_compare key_comp() const;
    constexpr value_compare value_comp() const;

    constexpr const key_container_type& keys() const noexcept { return /*c*/.keys; }
    constexpr const mapped_container_type& values() const noexcept
    {
      return /*c*/.values;
    }

    // map 操作
    constexpr iterator find(const key_type& x);
    constexpr const_iterator find(const key_type& x) const;
    template<class K> constexpr iterator find(const K& x);
    template<class K> constexpr const_iterator find(const K& x) const;

    constexpr size_type count(const key_type& x) const;
    template<class K> constexpr size_type count(const K& x) const;

    constexpr bool contains(const key_type& x) const;
    template<class K> constexpr bool contains(const K& x) const;

    constexpr iterator lower_bound(const key_type& x);
    constexpr const_iterator lower_bound(const key_type& x) const;
    template<class K> constexpr iterator lower_bound(const K& x);
    template<class K> constexpr const_iterator lower_bound(const K& x) const;

    constexpr iterator upper_bound(const key_type& x);
    constexpr const_iterator upper_bound(const key_type& x) const;
    template<class K> constexpr iterator upper_bound(const K& x);
    template<class K> constexpr const_iterator upper_bound(const K& x) const;

    constexpr pair<iterator, iterator> equal_range(const key_type& x);
    constexpr pair<const_iterator, const_iterator> equal_range(const key_type& x) const;
    template<class K> constexpr pair<iterator, iterator> equal_range(const K& x);
    template<class K>
    constexpr pair<const_iterator, const_iterator> equal_range(const K& x) const;

    friend constexpr bool operator==(const flat_map& x, const flat_map& y);

    friend constexpr /*synth-three-way-result*/<value_type> operator<=>(
      const flat_map& x, const flat_map& y);

    friend constexpr void swap(flat_map& x, flat_map& y) noexcept(noexcept(x.swap(y)))
    {
      x.swap(y);
    }

  private:
    containers /*c*/;        // 仅用于阐释
    key_compare /*compare*/; // 仅用于阐释

    struct /*key-equiv*/
	{                        // 仅用于阐释
      constexpr /*key-equiv*/(key_compare c)
        : comp(c)
      {
      }
      constexpr bool operator()(const_reference x, const_reference y) const
      {
        return !comp(x.first, y.first) && !comp(y.first, x.first);
      }
      key_compare comp;
    };
  };

  template<class KeyContainer,
           class MappedContainer,
           class Compare = less<typename KeyContainer::value_type>>
  flat_map(KeyContainer, MappedContainer, Compare = Compare())
    -> flat_map<typename KeyContainer::value_type,
                typename MappedContainer::value_type,
                Compare,
                KeyContainer,
                MappedContainer>;

  template<class KeyContainer, class MappedContainer, class Allocator>
  flat_map(KeyContainer, MappedContainer, Allocator)
    -> flat_map<typename KeyContainer::value_type,
                typename MappedContainer::value_type,
                less<typename KeyContainer::value_type>,
                KeyContainer,
                MappedContainer>;
  template<class KeyContainer, class MappedContainer, class Compare, class Allocator>
  flat_map(KeyContainer, MappedContainer, Compare, Allocator)
    -> flat_map<typename KeyContainer::value_type,
                typename MappedContainer::value_type,
                Compare,
                KeyContainer,
                MappedContainer>;

  template<class KeyContainer,
           class MappedContainer,
           class Compare = less<typename KeyContainer::value_type>>
  flat_map(sorted_unique_t, KeyContainer, MappedContainer, Compare = Compare())
    -> flat_map<typename KeyContainer::value_type,
                typename MappedContainer::value_type,
                Compare,
                KeyContainer,
                MappedContainer>;

  template<class KeyContainer, class MappedContainer, class Allocator>
  flat_map(sorted_unique_t, KeyContainer, MappedContainer, Allocator)
    -> flat_map<typename KeyContainer::value_type,
                typename MappedContainer::value_type,
                less<typename KeyContainer::value_type>,
                KeyContainer,
                MappedContainer>;
  template<class KeyContainer, class MappedContainer, class Compare, class Allocator>
  flat_map(sorted_unique_t, KeyContainer, MappedContainer, Compare, Allocator)
    -> flat_map<typename KeyContainer::value_type,
                typename MappedContainer::value_type,
                Compare,
                KeyContainer,
                MappedContainer>;

  template<class InputIter, class Compare = less</*iter-key-type*/<InputIter>>>
  flat_map(InputIter, InputIter, Compare = Compare())
    -> flat_map</*iter-key-type*/<InputIter>, /*iter-mapped-type*/<InputIter>, Compare>;

  template<class InputIter, class Compare = less</*iter-key-type*/<InputIter>>>
  flat_map(sorted_unique_t, InputIter, InputIter, Compare = Compare())
    -> flat_map</*iter-key-type*/<InputIter>, /*iter-mapped-type*/<InputIter>, Compare>;

  template<ranges::input_range R,
           class Compare = less</*range-key-type*/<R>>,
           class Allocator = allocator<byte>>
  flat_map(from_range_t, R&&, Compare = Compare(), Allocator = Allocator()) -> flat_map<
    /*range-key-type*/<R>,
    /*range-mapped-type*/<R>,
    Compare,
    vector</*range-key-type*/<R>, /*alloc-rebind*/<Allocator, /*range-key-type*/<R>>>,
    vector</*range-mapped-type*/<R>,
           /*alloc-rebind*/<Allocator, /*range-mapped-type*/<R>>>>;

  template<ranges::input_range R, class Allocator>
  flat_map(from_range_t, R&&, Allocator) -> flat_map<
    /*range-key-type*/<R>,
    /*range-mapped-type*/<R>,
    less</*range-key-type*/<R>>,
    vector</*range-key-type*/<R>, /*alloc-rebind*/<Allocator, /*range-key-type*/<R>>>,
    vector</*range-mapped-type*/<R>,
           /*alloc-rebind*/<Allocator, /*range-mapped-type*/<R>>>>;

  template<class Key, class T, class Compare = less<Key>>
  flat_map(initializer_list<pair<Key, T>>, Compare = Compare())
    -> flat_map<Key, T, Compare>;

  template<class Key, class T, class Compare = less<Key>>
  flat_map(sorted_unique_t, initializer_list<pair<Key, T>>, Compare = Compare())
    -> flat_map<Key, T, Compare>;

  template<class Key,
           class T,
           class Compare,
           class KeyContainer,
           class MappedContainer,
           class Allocator>
  struct uses_allocator<flat_map<Key, T, Compare, KeyContainer, MappedContainer>,
                        Allocator>
    : bool_constant<uses_allocator_v<KeyContainer, Allocator> &&
                    uses_allocator_v<MappedContainer, Allocator>>
  {};
}

类模板 `std::flat_multimap`

namespace std {
  template<class Key,
           class T,
           class Compare = less<Key>,
           class KeyContainer = vector<Key>,
           class MappedContainer = vector<T>>
  class flat_multimap
  {
  public:
    // 类型
    using key_type = Key;
    using mapped_type = T;
    using value_type = pair<key_type, mapped_type>;
    using key_compare = Compare;
    using reference = pair<const key_type&, mapped_type&>;
    using const_reference = pair<const key_type&, const mapped_type&>;
    using size_type = size_t;
    using difference_type = ptrdiff_t;
    using iterator = /* 由实现定义 */;
    using const_iterator = /* 由实现定义 */;
    using reverse_iterator = std::reverse_iterator<iterator>;
    using const_reverse_iterator = std::reverse_iterator<const_iterator>;
    using key_container_type = KeyContainer;
    using mapped_container_type = MappedContainer;

    class value_compare
    {
    private:
      key_compare /*comp*/; // 仅用于阐释
      constexpr value_compare(key_compare c)
        : /*comp*/(c)
      {
	  }                     // 仅用于阐释

    public:
      constexpr bool operator()(const_reference x, const_reference y) const
      {
        return /*comp*/(x.first, y.first);
      }
    };

    struct containers
    {
      key_container_type keys;
      mapped_container_type values;
    };

    // 构造函数
    constexpr flat_multimap()
      : flat_multimap(key_compare())
    {
    }

    constexpr flat_multimap(const flat_multimap&);
    constexpr flat_multimap(flat_multimap&&);
    constexpr flat_multimap& operator=(const flat_multimap&);
    constexpr flat_multimap& operator=(flat_multimap&&);

    constexpr explicit flat_multimap(const key_compare& comp)
      : /*c*/()
      , /*compare*/(comp)
    {
    }

    constexpr flat_multimap(key_container_type key_cont,
                            mapped_container_type mapped_cont,
                            const key_compare& comp = key_compare());

    constexpr flat_multimap(sorted_equivalent_t,
                            key_container_type key_cont,
                            mapped_container_type mapped_cont,
                            const key_compare& comp = key_compare());

    template<class InputIter>
    constexpr flat_multimap(InputIter first,
                            InputIter last,
                            const key_compare& comp = key_compare())
      : /*c*/()
      , /*compare*/(comp)
    {
      insert(first, last);
    }

    template<class InputIter>
    constexpr flat_multimap(sorted_equivalent_t,
                            InputIter first,
                            InputIter last,
                            const key_compare& comp = key_compare())
      : /*c*/()
      , /*compare*/(comp)
    {
      insert(sorted_equivalent, first, last);
    }

    template<container-compatible-range<value_type> R>
    constexpr flat_multimap(from_range_t, R&& rg)
      : flat_multimap(from_range, std::forward<R>(rg), key_compare())
    {
    }
    template<container-compatible-range<value_type> R>
    constexpr flat_multimap(from_range_t, R&& rg, const key_compare& comp)
      : flat_multimap(comp)
    {
      insert_range(std::forward<R>(rg));
    }

    constexpr flat_multimap(initializer_list<value_type> il,
                            const key_compare& comp = key_compare())
      : flat_multimap(il.begin(), il.end(), comp)
    {
    }

    constexpr flat_multimap(sorted_equivalent_t,
                            initializer_list<value_type> il,
                            const key_compare& comp = key_compare())
      : flat_multimap(sorted_equivalent, il.begin(), il.end(), comp)
    {
    }

    // 带分配器的构造函数

    template<class Alloc> constexpr explicit flat_multimap(const Alloc& a);
    template<class Alloc>
    constexpr flat_multimap(const key_compare& comp, const Alloc& a);
    template<class Alloc>
    constexpr flat_multimap(const key_container_type& key_cont,
                            const mapped_container_type& mapped_cont,
                            const Alloc& a);
    template<class Alloc>
    constexpr flat_multimap(const key_container_type& key_cont,
                            const mapped_container_type& mapped_cont,
                            const key_compare& comp,
                            const Alloc& a);
    template<class Alloc>
    constexpr flat_multimap(sorted_equivalent_t,
                            const key_container_type& key_cont,
                            const mapped_container_type& mapped_cont,
                            const Alloc& a);
    template<class Alloc>
    constexpr flat_multimap(sorted_equivalent_t,
                            const key_container_type& key_cont,
                            const mapped_container_type& mapped_cont,
                            const key_compare& comp,
                            const Alloc& a);
    template<class Alloc> constexpr flat_multimap(const flat_multimap&, const Alloc& a);
    template<class Alloc> constexpr flat_multimap(flat_multimap&&, const Alloc& a);
    template<class InputIter, class Alloc>
    constexpr flat_multimap(InputIter first, InputIter last, const Alloc& a);
    template<class InputIter, class Alloc>
    constexpr flat_multimap(InputIter first,
                            InputIter last,
                            const key_compare& comp,
                            const Alloc& a);
    template<class InputIter, class Alloc>
    constexpr flat_multimap(sorted_equivalent_t,
                            InputIter first,
                            InputIter last,
                            const Alloc& a);
    template<class InputIter, class Alloc>
    constexpr flat_multimap(sorted_equivalent_t,
                            InputIter first,
                            InputIter last,
                            const key_compare& comp,
                            const Alloc& a);
    template<container-compatible-range<value_type> R, class Alloc>
    constexpr flat_multimap(from_range_t, R&& rg, const Alloc& a);
    template<container-compatible-range<value_type> R, class Alloc>
    constexpr flat_multimap(from_range_t,
                            R&& rg,
                            const key_compare& comp,
                            const Alloc& a);
    template<class Alloc>
    constexpr flat_multimap(initializer_list<value_type> il, const Alloc& a);
    template<class Alloc>
    constexpr flat_multimap(initializer_list<value_type> il,
                            const key_compare& comp,
                            const Alloc& a);
    template<class Alloc>
    constexpr flat_multimap(sorted_equivalent_t,
                            initializer_list<value_type> il,
                            const Alloc& a);
    template<class Alloc>
    constexpr flat_multimap(sorted_equivalent_t,
                            initializer_list<value_type> il,
                            const key_compare& comp,
                            const Alloc& a);

    flat_multimap& operator=(initializer_list<value_type>);

    // 迭代器
    constexpr iterator begin() noexcept;
    constexpr const_iterator begin() const noexcept;
    constexpr iterator end() noexcept;
    constexpr const_iterator end() const noexcept;

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

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

    // 容量
    constexpr bool empty() const noexcept;
    constexpr size_type size() const noexcept;
    constexpr size_type max_size() const noexcept;

    // 修改器
    template<class... Args> constexpr iterator emplace(Args&&... args);
    template<class... Args>
    constexpr iterator emplace_hint(const_iterator position, Args&&... args);

    constexpr iterator insert(const value_type& x) { return emplace(x); }
    constexpr iterator insert(value_type&& x) { return emplace(std::move(x)); }
    constexpr iterator insert(const_iterator position, const value_type& x)
    {
      return emplace_hint(position, x);
    }
    constexpr iterator insert(const_iterator position, value_type&& x)
    {
      return emplace_hint(position, std::move(x));
    }

    template<class P> constexpr iterator insert(P&& x);
    template<class P> constexpr iterator insert(const_iterator position, P&&);
    template<class InputIter> constexpr void insert(InputIter first, InputIter last);
    template<class InputIter>
    constexpr void insert(sorted_equivalent_t, InputIter first, InputIter last);
    template<container-compatible-range<value_type> R>
    constexpr void insert_range(R&& rg);
    template<container-compatible-range<value_type> R>
    constexpr void insert_range(sorted_equivalent_t, R&& rg);

    constexpr void insert(initializer_list<value_type> il)
    {
      insert(il.begin(), il.end());
    }
    constexpr void insert(sorted_equivalent_t, initializer_list<value_type> il)
    {
      insert(sorted_equivalent, il.begin(), il.end());
    }

    constexpr containers extract() &&;
    constexpr void replace(key_container_type&& key_cont,
                           mapped_container_type&& mapped_cont);

    constexpr iterator erase(iterator position);
    constexpr iterator erase(const_iterator position);
    constexpr size_type erase(const key_type& x);
    template<class K> constexpr size_type erase(K&& x);
    constexpr iterator erase(const_iterator first, const_iterator last);

    constexpr void swap(flat_multimap&) noexcept(
      is_nothrow_swappable_v<key_container_type>&& is_nothrow_swappable_v<
        mapped_container_type>&& is_nothrow_swappable_v<key_compare>);
    constexpr void clear() noexcept;

    // 观察器
    constexpr key_compare key_comp() const;
    constexpr value_compare value_comp() const;

    constexpr const key_container_type& keys() const noexcept { return /*c*/.keys; }
    constexpr const mapped_container_type& values() const noexcept
    {
      return /*c*/.values;
    }

    // map 操作
    constexpr iterator find(const key_type& x);
    constexpr const_iterator find(const key_type& x) const;
    template<class K> constexpr iterator find(const K& x);
    template<class K> constexpr const_iterator find(const K& x) const;

    constexpr size_type count(const key_type& x) const;
    template<class K> constexpr size_type count(const K& x) const;

    constexpr bool contains(const key_type& x) const;
    template<class K> constexpr bool contains(const K& x) const;

    constexpr iterator lower_bound(const key_type& x);
    constexpr const_iterator lower_bound(const key_type& x) const;
    template<class K> constexpr iterator lower_bound(const K& x);
    template<class K> constexpr const_iterator lower_bound(const K& x) const;

    constexpr iterator upper_bound(const key_type& x);
    constexpr const_iterator upper_bound(const key_type& x) const;
    template<class K> constexpr iterator upper_bound(const K& x);
    template<class K> constexpr const_iterator upper_bound(const K& x) const;

    constexpr pair<iterator, iterator> equal_range(const key_type& x);
    constexpr pair<const_iterator, const_iterator> equal_range(const key_type& x) const;
    template<class K> constexpr pair<iterator, iterator> equal_range(const K& x);
    template<class K>
    constexpr pair<const_iterator, const_iterator> equal_range(const K& x) const;

    friend constexpr bool operator==(const flat_multimap& x, const flat_multimap& y);

    friend constexpr /*synth-three-way-result*/<value_type> operator<=>(
      const flat_multimap& x, const flat_multimap& y);

    friend constexpr void swap(flat_multimap& x,
                               flat_multimap& y) noexcept(noexcept(x.swap(y)))
    {
      x.swap(y);
    }

  private:
    containers /*c*/;        // 仅用于阐释
    key_compare /*compare*/; // 仅用于阐释
  };

  template<class KeyContainer,
           class MappedContainer,
           class Compare = less<typename KeyContainer::value_type>>
  flat_multimap(KeyContainer, MappedContainer, Compare = Compare())
    -> flat_multimap<typename KeyContainer::value_type,
                     typename MappedContainer::value_type,
                     Compare,
                     KeyContainer,
                     MappedContainer>;

  template<class KeyContainer, class MappedContainer, class Allocator>
  flat_multimap(KeyContainer, MappedContainer, Allocator)
    -> flat_multimap<typename KeyContainer::value_type,
                     typename MappedContainer::value_type,
                     less<typename KeyContainer::value_type>,
                     KeyContainer,
                     MappedContainer>;
  template<class KeyContainer, class MappedContainer, class Compare, class Allocator>
  flat_multimap(KeyContainer, MappedContainer, Compare, Allocator)
    -> flat_multimap<typename KeyContainer::value_type,
                     typename MappedContainer::value_type,
                     Compare,
                     KeyContainer,
                     MappedContainer>;

  template<class KeyContainer,
           class MappedContainer,
           class Compare = less<typename KeyContainer::value_type>>
  flat_multimap(sorted_equivalent_t, KeyContainer, MappedContainer, Compare = Compare())
    -> flat_multimap<typename KeyContainer::value_type,
                     typename MappedContainer::value_type,
                     Compare,
                     KeyContainer,
                     MappedContainer>;

  template<class KeyContainer, class MappedContainer, class Allocator>
  flat_multimap(sorted_equivalent_t, KeyContainer, MappedContainer, Allocator)
    -> flat_multimap<typename KeyContainer::value_type,
                     typename MappedContainer::value_type,
                     less<typename KeyContainer::value_type>,
                     KeyContainer,
                     MappedContainer>;
  template<class KeyContainer, class MappedContainer, class Compare, class Allocator>
  flat_multimap(sorted_equivalent_t, KeyContainer, MappedContainer, Compare, Allocator)
    -> flat_multimap<typename KeyContainer::value_type,
                     typename MappedContainer::value_type,
                     Compare,
                     KeyContainer,
                     MappedContainer>;

  template<class InputIter, class Compare = less</*iter-key-type*/<InputIter>>>
  flat_multimap(InputIter, InputIter, Compare = Compare())
    -> flat_multimap</*iter-key-type*/<InputIter>,
                     /*iter-mapped-type*/<InputIter>,
                     Compare>;

  template<class InputIter, class Compare = less</*iter-key-type*/<InputIter>>>
  flat_multimap(sorted_equivalent_t, InputIter, InputIter, Compare = Compare())
    -> flat_multimap</*iter-key-type*/<InputIter>,
                     /*iter-mapped-type*/<InputIter>,
                     Compare>;

  template<ranges::input_range R,
           class Compare = less</*range-key-type*/<R>>,
           class Allocator = allocator<byte>>
  flat_multimap(from_range_t, R&&, Compare = Compare(), Allocator = Allocator())
    -> flat_multimap<
      /*range-key-type*/<R>,
      /*range-mapped-type*/<R>,
      Compare,
      vector</*range-key-type*/<R>, /*alloc-rebind*/<Allocator, /*range-key-type*/<R>>>,
      vector</*range-mapped-type*/<R>,
             /*alloc-rebind*/<Allocator, /*range-mapped-type*/<R>>>>;

  template<ranges::input_range R, class Allocator>
  flat_multimap(from_range_t, R&&, Allocator) -> flat_multimap<
    /*range-key-type*/<R>,
    /*range-mapped-type*/<R>,
    less</*range-key-type*/<R>>,
    vector</*range-key-type*/<R>, /*alloc-rebind*/<Allocator, /*range-key-type*/<R>>>,
    vector</*range-mapped-type*/<R>,
           /*alloc-rebind*/<Allocator, /*range-mapped-type*/<R>>>>;

  template<class Key, class T, class Compare = less<Key>>
  flat_multimap(initializer_list<pair<Key, T>>, Compare = Compare())
    -> flat_multimap<Key, T, Compare>;

  template<class Key, class T, class Compare = less<Key>>
  flat_multimap(sorted_equivalent_t, initializer_list<pair<Key, T>>, Compare = Compare())
    -> flat_multimap<Key, T, Compare>;

  template<class Key,
           class T,
           class Compare,
           class KeyContainer,
           class MappedContainer,
           class Allocator>
  struct uses_allocator<flat_multimap<Key, T, Compare, KeyContainer, MappedContainer>,
                        Allocator>
    : bool_constant<uses_allocator_v<KeyContainer, Allocator> &&
                    uses_allocator_v<MappedContainer, Allocator>>
  {};
}

引用

C++23 标准（ISO/IEC 14882:2024）：

24.6.4 Header <flat_map> synopsis [flat.map.syn]

24.6.9.2 Definition [flat.map.defn]

24.6.10.2 Definition [flat.multimap.defn]

标准库标头 <flat_map> (C++23) - cppreference.com

包含

类

函数

标签

概要

类模板 std::flat_map

类模板 std::flat_multimap

引用

类模板 `std::flat_map`

类模板 `std::flat_multimap`