标准库标头 <map>

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标准库标头
注：修订记号中的反斜杠 '/' 意味着此标头被弃用和/或被移除。
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概念
<concepts> (C++20)
诊断
<system_error> (C++11)
内存管理
<memory_resource> (C++17)  
元编程
<type_traits> (C++11)
<ratio> (C++11)
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<utility>
<tuple> (C++11)
<optional> (C++17)
<variant> (C++17)
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<bitset>

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字符串
<cuchar> (C++11)

容器
<flat_set> (C++23)
<span> (C++20)
<mdspan> (C++23)

迭代器
<iterator>
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并发支持
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C 兼容
<cstdbool> (C++11/17/20)  
<ccomplex> (C++11/17/20)
<ctgmath> (C++11/17/20)

<cstdalign> (C++11/17/20)

<ciso646> (C++20 前)

 

此标头是容器库的一部分。

包含

(C++20)
 三路比较运算符支持
(C++11)
 std::initializer_list 类模板

类

 键值对的集合，按照键排序，键是唯一的
(类模板)
键值对的集合，按照键排序
(类模板)

函数

(C++20 中移除)(C++20 中移除)(C++20 中移除)(C++20 中移除)(C++20 中移除)(C++20)
 按照字典顺序比较 map 中的值
(函数模板)
特化 std::swap 算法
(函数模板)
(C++20)
 擦除所有满足特定判别标准的元素
(函数模板)
(C++20 中移除)(C++20 中移除)(C++20 中移除)(C++20 中移除)(C++20 中移除)(C++20)
 按照字典顺序比较 multimap 中的值
(函数模板)
特化 std::swap 算法
(函数模板)
(C++20)
 擦除所有满足特定判别标准的元素
(函数模板)
范围访问
(C++11)(C++14)
 返回指向容器或数组起始的迭代器
(函数模板)
(C++11)(C++14)
 返回指向容器或数组结尾的迭代器
(函数模板)
(C++14)
 返回指向一个容器或数组的逆向迭代器
(函数模板)
(C++14)
 返回容器或数组的逆向尾迭代器
(函数模板)
(C++17)(C++20)
 返回容器或数组的大小
(函数模板)
(C++17)
 检查容器是否为空
(函数模板)
(C++17)
 获得指向底层数组的指针
(函数模板)

概要

#include <compare>
#include <initializer_list>
 
namespace std {
  // 类模板 map
  template<class Key, class T, class Compare = less<Key>,
           class Allocator = allocator<pair<const Key, T>>>
    class map;
 
  template<class Key, class T, class Compare, class Allocator>
    bool operator==(const map<Key, T, Compare, Allocator>& x,
                    const map<Key, T, Compare, Allocator>& y);
  template<class Key, class T, class Compare, class Allocator>
    /*synth-three-way-result*/<pair<const Key, T>>
      operator<=>(const map<Key, T, Compare, Allocator>& x,
                  const map<Key, T, Compare, Allocator>& y);
 
  template<class Key, class T, class Compare, class Allocator>
    void swap(map<Key, T, Compare, Allocator>& x,
              map<Key, T, Compare, Allocator>& y)
      noexcept(noexcept(x.swap(y)));
 
  template<class Key, class T, class Compare, class Allocator, class Predicate>
    typename map<Key, T, Compare, Allocator>::size_type
      erase_if(map<Key, T, Compare, Allocator>& c, Predicate pred);
 
  // 类模板 multimap
  template<class Key, class T, class Compare = less<Key>,
           class Allocator = allocator<pair<const Key, T>>>
    class multimap;
 
  template<class Key, class T, class Compare, class Allocator>
    bool operator==(const multimap<Key, T, Compare, Allocator>& x,
                    const multimap<Key, T, Compare, Allocator>& y);
  template<class Key, class T, class Compare, class Allocator>
    /*synth-three-way-result*/<pair<const Key, T>>
      operator<=>(const multimap<Key, T, Compare, Allocator>& x,
                  const multimap<Key, T, Compare, Allocator>& y);
 
  template<class Key, class T, class Compare, class Allocator>
    void swap(multimap<Key, T, Compare, Allocator>& x,
              multimap<Key, T, Compare, Allocator>& y)
      noexcept(noexcept(x.swap(y)));
 
  template<class Key, class T, class Compare, class Allocator, class Predicate>
    typename multimap<Key, T, Compare, Allocator>::size_type
      erase_if(multimap<Key, T, Compare, Allocator>& c, Predicate pred);
 
  namespace pmr {
    template<class Key, class T, class Compare = less<Key>>
      using map = std::map<Key, T, Compare,
                           polymorphic_allocator<pair<const Key, T>>>;
 
    template<class Key, class T, class Compare = less<Key>>
      using multimap = std::multimap<Key, T, Compare,
                                     polymorphic_allocator<pair<const Key, T>>>;
  }
}

类模板 std::map

namespace std {
  template<class Key, class T, class Compare = less<Key>,
           class Allocator = allocator<pair<const Key, T>>>
  class map {
  public:
    // 类型
    using key_type               = Key;
    using mapped_type            = T;
    using value_type             = pair<const Key, T>;
    using key_compare            = Compare;
    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              = /* 由实现定义 */;
    using difference_type        = /* 由实现定义 */;
    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 node_type              = /* 未指明 */;
    using insert_return_type     = /*insert-return-type*/<iterator, node_type>;
 
    class value_compare {
      friend class map;
    protected:
      Compare comp;
      value_compare(Compare c) : comp(c) {}
    public:
      bool operator()(const value_type& x, const value_type& y) const {
        return comp(x.first, y.first);
      }
    };
 
    // 构造/复制/销毁
    map() : map(Compare()) { }
    explicit map(const Compare& comp, const Allocator& = Allocator());
    template<class InputIt>
      map(InputIt first, InputIt last,
          const Compare& comp = Compare(), const Allocator& = Allocator());
    map(const map& x);
    map(map&& x);
    explicit map(const Allocator&);
    map(const map&, const Allocator&);
    map(map&&, const Allocator&);
    map(initializer_list<value_type>,
      const Compare& = Compare(),
      const Allocator& = Allocator());
    template<class InputIt>
      map(InputIt first, InputIt last, const Allocator& a)
        : map(first, last, Compare(), a) { }
    map(initializer_list<value_type> il, const Allocator& a)
      : map(il, Compare(), a) { }
    ~map();
    map& operator=(const map& x);
    map& operator=(map&& x)
      noexcept(allocator_traits<Allocator>::is_always_equal::value &&
               is_nothrow_move_assignable_v<Compare>);
    map& operator=(initializer_list<value_type>);
    allocator_type get_allocator() const noexcept;
 
    // 迭代器
    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;
 
    // 容量
    [[nodiscard]] bool empty() const noexcept;
    size_type size() const noexcept;
    size_type max_size() const noexcept;
 
    // 元素访问
    mapped_type& operator[](const key_type& x);
    mapped_type& operator[](key_type&& x);
    mapped_type&       at(const key_type& x);
    const mapped_type& at(const key_type& x) const;
 
    // 修改器
    template<class... Args> pair<iterator, bool> emplace(Args&&... args);
    template<class... Args> iterator emplace_hint(const_iterator position, Args&&... args);
    pair<iterator, bool> insert(const value_type& x);
    pair<iterator, bool> insert(value_type&& x);
    template<class P> pair<iterator, bool> insert(P&& x);
    iterator insert(const_iterator position, const value_type& x);
    iterator insert(const_iterator position, value_type&& x);
    template<class P>
      iterator insert(const_iterator position, P&&);
    template<class InputIt>
      void insert(InputIt first, InputIt last);
    void insert(initializer_list<value_type>);
 
    node_type extract(const_iterator position);
    node_type extract(const key_type& x);
    template<class K> node_type extract(K&& x);
    insert_return_type insert(node_type&& nh);
    iterator           insert(const_iterator hint, node_type&& nh);
 
    template<class... Args>
      pair<iterator, bool> try_emplace(const key_type& k, Args&&... args);
    template<class... Args>
      pair<iterator, bool> try_emplace(key_type&& k, Args&&... args);
    template<class... Args>
      iterator try_emplace(const_iterator hint, const key_type& k, Args&&... args);
    template<class... Args>
      iterator try_emplace(const_iterator hint, key_type&& k, Args&&... args);
    template<class M>
      pair<iterator, bool> insert_or_assign(const key_type& k, M&& obj);
    template<class M>
      pair<iterator, bool> insert_or_assign(key_type&& k, M&& obj);
    template<class M>
      iterator insert_or_assign(const_iterator hint, const key_type& k, M&& obj);
    template<class M>
      iterator insert_or_assign(const_iterator hint, key_type&& k, M&& obj);
 
    iterator  erase(iterator position);
    iterator  erase(const_iterator position);
    size_type erase(const key_type& x);
    template<class K> size_type erase(K&& x);
    iterator  erase(const_iterator first, const_iterator last);
    void      swap(map&)
      noexcept(allocator_traits<Allocator>::is_always_equal::value &&
               is_nothrow_swappable_v<Compare>);
    void      clear() noexcept;
 
    template<class C2>
      void merge(map<Key, T, C2, Allocator>& source);
    template<class C2>
      void merge(map<Key, T, C2, Allocator>&& source);
    template<class C2>
      void merge(multimap<Key, T, C2, Allocator>& source);
    template<class C2>
      void merge(multimap<Key, T, C2, Allocator>&& source);
 
    // 观察器
    key_compare key_comp() const;
    value_compare value_comp() const;
 
    // map 操作
    iterator       find(const key_type& x);
    const_iterator find(const key_type& x) const;
    template<class K> iterator       find(const K& x);
    template<class K> const_iterator find(const K& x) const;
 
    size_type      count(const key_type& x) const;
    template<class K> size_type count(const K& x) const;
 
    bool           contains(const key_type& x) const;
    template<class K> bool contains(const K& x) const;
 
    iterator       lower_bound(const key_type& x);
    const_iterator lower_bound(const key_type& x) const;
    template<class K> iterator       lower_bound(const K& x);
    template<class K> const_iterator lower_bound(const K& x) const;
 
    iterator       upper_bound(const key_type& x);
    const_iterator upper_bound(const key_type& x) const;
    template<class K> iterator       upper_bound(const K& x);
    template<class K> const_iterator upper_bound(const K& 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 K>
      pair<iterator, iterator>             equal_range(const K& x);
    template<class K>
      pair<const_iterator, const_iterator> equal_range(const K& x) const;
  };
 
  template<class InputIt, class Compare = less</*iter-key-type*/<InputIt>>,
           class Allocator = allocator</*iter-to-alloc-type*/<InputIt>>>
    map(InputIt, InputIt, Compare = Compare(), Allocator = Allocator())
      -> map</*iter-key-type*/<InputIt>, /*iter-mapped-type*/<InputIt>,
             Compare, Allocator>;
 
  template<class Key, class T, class Compare = less<Key>,
           class Allocator = allocator<pair<const Key, T>>>
    map(initializer_list<pair<Key, T>>, Compare = Compare(), Allocator = Allocator())
      -> map<Key, T, Compare, Allocator>;
 
  template<class InputIt, class Allocator>
    map(InputIt, InputIt, Allocator)
      -> map</*iter-key-type*/<InputIt>, /*iter-mapped-type*/<InputIt>,
             less</*iter-key-type*/<InputIt>>, Allocator>;
 
  template<class Key, class T, class Allocator>
    map(initializer_list<pair<Key, T>>, Allocator) -> map<Key, T, less<Key>, Allocator>;
 
  // 交换
  template<class Key, class T, class Compare, class Allocator>
    void swap(map<Key, T, Compare, Allocator>& x,
              map<Key, T, Compare, Allocator>& y)
      noexcept(noexcept(x.swap(y)));
}

类模板 std::multimap

namespace std {
  template<class Key, class T, class Compare = less<Key>,
           class Allocator = allocator<pair<const Key, T>>>
  class multimap {
  public:
    // 类型
    using key_type               = Key;
    using mapped_type            = T;
    using value_type             = pair<const Key, T>;
    using key_compare            = Compare;
    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              = /* 由实现定义 */;
    using difference_type        = /* 由实现定义 */;
    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 node_type              = /* 未指明 */;
 
    class value_compare {
      friend class multimap;
    protected:
      Compare comp;
      value_compare(Compare c) : comp(c) { }
    public:
      bool operator()(const value_type& x, const value_type& y) const {
        return comp(x.first, y.first);
      }
    };
 
    // 构造/复制/销毁
    multimap() : multimap(Compare()) { }
    explicit multimap(const Compare& comp, const Allocator& = Allocator());
    template<class InputIt>
      multimap(InputIt first, InputIt last,
               const Compare& comp = Compare(),
               const Allocator& = Allocator());
    multimap(const multimap& x);
    multimap(multimap&& x);
    explicit multimap(const Allocator&);
    multimap(const multimap&, const Allocator&);
    multimap(multimap&&, const Allocator&);
    multimap(initializer_list<value_type>,
      const Compare& = Compare(),
      const Allocator& = Allocator());
    template<class InputIt>
      multimap(InputIt first, InputIt last, const Allocator& a)
        : multimap(first, last, Compare(), a) { }
    multimap(initializer_list<value_type> il, const Allocator& a)
      : multimap(il, Compare(), a) { }
    ~multimap();
    multimap& operator=(const multimap& x);
    multimap& operator=(multimap&& x)
      noexcept(allocator_traits<Allocator>::is_always_equal::value &&
               is_nothrow_move_assignable_v<Compare>);
    multimap& operator=(initializer_list<value_type>);
    allocator_type get_allocator() const noexcept;
 
    // 迭代器
    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;
 
    // 容量
    [[nodiscard]] bool empty() const noexcept;
    size_type size() const noexcept;
    size_type max_size() const noexcept;
 
    // 修改器
    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);
    template<class P> iterator insert(P&& x);
    iterator insert(const_iterator position, const value_type& x);
    iterator insert(const_iterator position, value_type&& x);
    template<class P> iterator insert(const_iterator position, P&& x);
    template<class InputIt>
      void insert(InputIt first, InputIt last);
    void insert(initializer_list<value_type>);
 
    node_type extract(const_iterator position);
    node_type extract(const key_type& x);
    template<class K> node_type extract(K&& 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& x);
    template<class K> size_type erase(K&& x);
    iterator  erase(const_iterator first, const_iterator last);
    void      swap(multimap&)
      noexcept(allocator_traits<Allocator>::is_always_equal::value &&
               is_nothrow_swappable_v<Compare>);
    void      clear() noexcept;
 
    template<class C2>
      void merge(multimap<Key, T, C2, Allocator>& source);
    template<class C2>
      void merge(multimap<Key, T, C2, Allocator>&& source);
    template<class C2>
      void merge(map<Key, T, C2, Allocator>& source);
    template<class C2>
      void merge(map<Key, T, C2, Allocator>&& source);
 
    // 观察器
    key_compare key_comp() const;
    value_compare value_comp() const;
 
    // map 操作
    iterator       find(const key_type& x);
    const_iterator find(const key_type& x) const;
    template<class K> iterator       find(const K& x);
    template<class K> const_iterator find(const K& x) const;
 
    size_type      count(const key_type& x) const;
    template<class K> size_type count(const K& x) const;
 
    bool           contains(const key_type& x) const;
    template<class K> bool contains(const K& x) const;
 
    iterator       lower_bound(const key_type& x);
    const_iterator lower_bound(const key_type& x) const;
    template<class K> iterator       lower_bound(const K& x);
    template<class K> const_iterator lower_bound(const K& x) const;
 
    iterator       upper_bound(const key_type& x);
    const_iterator upper_bound(const key_type& x) const;
    template<class K> iterator       upper_bound(const K& x);
    template<class K> const_iterator upper_bound(const K& 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 K>
      pair<iterator, iterator>             equal_range(const K& x);
    template<class K>
      pair<const_iterator, const_iterator> equal_range(const K& x) const;
  };
 
  template<class InputIt, class Compare = less</*iter-key-type*/<InputIt>>,
           class Allocator = allocator</*iter-to-alloc-type*/<InputIt>>>
    multimap(InputIt, InputIt, Compare = Compare(), Allocator = Allocator())
      -> multimap</*iter-key-type*/<InputIt>, /*iter-mapped-type*/<InputIt>,
                  Compare, Allocator>;
 
  template<class Key, class T, class Compare = less<Key>,
           class Allocator = allocator<pair<const Key, T>>>
    multimap(initializer_list<pair<Key, T>>, Compare = Compare(), Allocator = Allocator())
      -> multimap<Key, T, Compare, Allocator>;
 
  template<class InputIt, class Allocator>
    multimap(InputIt, InputIt, Allocator)
      -> multimap</*iter-key-type*/<InputIt>, /*iter-mapped-type*/<InputIt>,
                  less</*iter-key-type*/<InputIt>>, Allocator>;
 
  template<class Key, class T, class Allocator>
    multimap(initializer_list<pair<Key, T>>, Allocator)
      -> multimap<Key, T, less<Key>, Allocator>;
 
  // 交换
  template<class Key, class T, class Compare, class Allocator>
    void swap(multimap<Key, T, Compare, Allocator>& x,
              multimap<Key, T, Compare, Allocator>& y)
      noexcept(noexcept(x.swap(y)));
}

缺陷报告

下列更改行为的缺陷报告追溯地应用于以前出版的 C++ 标准。

缺陷报告 应用于 出版时的行为 正确行为
LWG 133 C++98 概要中缺失了 map::get_allocator 已补充
来自“https://zh.cppreference.com/mwiki/index.php?title=cpp/header/map&oldid=74990”