# 标准库头文件 <vector>

< cpp‎ | header

此头文件是容器库的一部分。

### 包含
<compare> (C++20) | 三路比较运算符支持
<initializer_list> (C++11) | std::initializer_list 类模板
### 类
vector | 动态的连续数组 (类模板)
vector<bool> | 节省空间的动态 bitset (类模板特化)
std::hash<std::vector<bool>> (C++11) | std::vector<bool> 的散列支持 (类模板特化)
##### 前置声明
定义于头文件 `<functional>`
hash (C++11) | 散列函数对象 (类模板)
### 函数
operator==operator!=operator<operator<=operator>operator>=operator<=> (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 vector 中的值 (函数模板)
std::swap(std::vector) | 特化 std::swap 算法 (函数模板)
erase(std::vector)erase_if(std::vector) (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
begin cbegin (C++11)(C++14) | 返回指向容器或数组起始的迭代器 (函数模板)
end cend (C++11)(C++14) | 返回指向容器或数组结尾的迭代器 (函数模板)
rbegin crbegin (C++14) | 返回指向一个容器或数组的逆向迭代器 (函数模板)
rend crend (C++14) | 返回容器或数组的逆向尾迭代器 (函数模板)
size ssize (C++17)(C++20) | 返回容器或数组的大小 (函数模板)
empty (C++17) | 检查容器是否为空 (函数模板)
data (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 vector
      template<class T, class Allocator = allocator<T>> class vector;

      template<class T, class Allocator>
        constexpr bool operator==(const vector<T, Allocator>& x,
                                  const vector<T, Allocator>& y);
      template<class T, class Allocator>
        constexpr /*synth-three-way-result*/<T> operator<=>(const vector<T, Allocator>& x,
                                                            const vector<T, Allocator>& y);

      template<class T, class Allocator>
        constexpr void swap(vector<T, Allocator>& x, vector<T, Allocator>& y)
          noexcept(noexcept(x.swap(y)));

      template<class T, class Allocator, class U>
        constexpr typename vector<T, Allocator>::size_type
          erase(vector<T, Allocator>& c, const U& value);
      template<class T, class Allocator, class Predicate>
        constexpr typename vector<T, Allocator>::size_type
          erase_if(vector<T, Allocator>& c, Predicate pred);

      // 类 vector<bool>
      template<class Allocator> class vector<bool, Allocator>;

      // 散列支持
      template<class T> struct hash;
      template<class Allocator> struct hash<vector<bool, Allocator>>;

      namespace pmr {
        template<class T>
          using vector = std::vector<T, polymorphic_allocator<T>>;
      }
    }

#### 类模板 std::vector

    namespace std {
      template<class T, class Allocator = allocator<T>>
      class vector {
      public:
        // 类型
        using value_type             = T;
        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>;

        // 构造/复制/销毁
        constexpr vector() noexcept(noexcept(Allocator())) : vector(Allocator()) { }
        constexpr explicit vector(const Allocator&) noexcept;
        constexpr explicit vector(size_type n, const Allocator& = Allocator());
        constexpr vector(size_type n, const T& value, const Allocator& = Allocator());
        template<class InputIt>
          constexpr vector(InputIt first, InputIt last, const Allocator& = Allocator());
        constexpr vector(const vector& x);
        constexpr vector(vector&&) noexcept;
        constexpr vector(const vector&, const Allocator&);
        constexpr vector(vector&&, const Allocator&);
        constexpr vector(initializer_list<T>, const Allocator& = Allocator());
        constexpr ~vector();
        constexpr vector& operator=(const vector& x);
        constexpr vector& operator=(vector&& x)
          noexcept(allocator_traits<Allocator>::propagate_on_container_move_assignment::value ||
                   allocator_traits<Allocator>::is_always_equal::value);
        constexpr vector& operator=(initializer_list<T>);
        template<class InputIt>
          constexpr void assign(InputIt first, InputIt last);
        constexpr void assign(size_type n, const T& u);
        constexpr void assign(initializer_list<T>);
        constexpr allocator_type get_allocator() const noexcept;

        // 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
        [[nodiscard]] constexpr bool empty() const noexcept;
        constexpr size_type size() const noexcept;
        constexpr size_type max_size() const noexcept;
        constexpr size_type capacity() const noexcept;
        constexpr void      resize(size_type sz);
        constexpr void      resize(size_type sz, const T& c);
        constexpr void      reserve(size_type n);
        constexpr void      shrink_to_fit();

        // 元素访问
        constexpr reference       operator[](size_type n);
        constexpr const_reference operator[](size_type n) const;
        constexpr const_reference at(size_type n) const;
        constexpr reference       at(size_type n);
        constexpr reference       front();
        constexpr const_reference front() const;
        constexpr reference       back();
        constexpr const_reference back() const;

        // 数据访问
        constexpr T*       data() noexcept;
        constexpr const T* data() const noexcept;

        // 修改器
        template<class... Args> constexpr reference emplace_back(Args&&... args);
        constexpr void push_back(const T& x);
        constexpr void push_back(T&& x);
        constexpr void pop_back();

        template<class... Args>
          constexpr iterator emplace(const_iterator position, Args&&... args);
        constexpr iterator insert(const_iterator position, const T& x);
        constexpr iterator insert(const_iterator position, T&& x);
        constexpr iterator insert(const_iterator position, size_type n, const T& x);
        template<class InputIt>
          constexpr iterator insert(const_iterator position,
                                    InputIt first, InputIt last);
        constexpr iterator insert(const_iterator position, initializer_list<T> il);
        constexpr iterator erase(const_iterator position);
        constexpr iterator erase(const_iterator first, const_iterator last);
        constexpr void     swap(vector&)
          noexcept(allocator_traits<Allocator>::propagate_on_container_swap::value ||
                   allocator_traits<Allocator>::is_always_equal::value);
        constexpr void     clear() noexcept;
      };

      template<class InputIt, class Allocator = allocator</*iter-value-type*/<InputIt>>>
        vector(InputIt, InputIt, Allocator = Allocator())
          -> vector</*iter-value-type*/<InputIt>, Allocator>;

      // 交换
      template<class T, class Allocator>
        constexpr void swap(vector<T, Allocator>& x, vector<T, Allocator>& y)
          noexcept(noexcept(x.swap(y)));
    }

#### 类模板 std::vector 对 bool 的特化

    namespace std {
      template<class Allocator>
      class vector<bool, Allocator> {
      public:
        // 类型
        using value_type             = bool;
        using allocator_type         = Allocator;
        using pointer                = /* 由实现定义 */;
        using const_pointer          = /* 由实现定义 */;
        using const_reference        = bool;
        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>;

        // 位引用
        class reference {
          friend class vector;
          constexpr reference() noexcept;
        public:
          constexpr reference(const reference&) = default;
          constexpr ~reference();
          constexpr operator bool() const noexcept;
          constexpr reference& operator=(const bool x) noexcept;
          constexpr reference& operator=(const reference& x) noexcept;
          constexpr void flip() noexcept;   // 翻转位
        };

        // 构造/复制/销毁
        constexpr vector() : vector(Allocator()) { }
        constexpr explicit vector(const Allocator&);
        constexpr explicit vector(size_type n, const Allocator& = Allocator());
        constexpr vector(size_type n, const bool& value, const Allocator& = Allocator());
        template<class InputIt>
          constexpr vector(InputIt first, InputIt last, const Allocator& = Allocator());
        constexpr vector(const vector& x);
        constexpr vector(vector&& x);
        constexpr vector(const vector&, const Allocator&);
        constexpr vector(vector&&, const Allocator&);
        constexpr vector(initializer_list<bool>, const Allocator& = Allocator()));
        constexpr ~vector();
        constexpr vector& operator=(const vector& x);
        constexpr vector& operator=(vector&& x);
        constexpr vector& operator=(initializer_list<bool>);
        template<class InputIt>
          constexpr void assign(InputIt first, InputIt last);
        constexpr void assign(size_type n, const bool& t);
        constexpr void assign(initializer_list<bool>);
        constexpr allocator_type get_allocator() const noexcept;

        // 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
        [[nodiscard]] constexpr bool empty() const noexcept;
        constexpr size_type size() const noexcept;
        constexpr size_type max_size() const noexcept;
        constexpr size_type capacity() const noexcept;
        constexpr void      resize(size_type sz, bool c = false);
        constexpr void      reserve(size_type n);
        constexpr void      shrink_to_fit();

        // 元素访问
        constexpr reference       operator[](size_type n);
        constexpr const_reference operator[](size_type n) const;
        constexpr const_reference at(size_type n) const;
        constexpr reference       at(size_type n);
        constexpr reference       front();
        constexpr const_reference front() const;
        constexpr reference       back();
        constexpr const_reference back() const;

        // 修改器
        template<class... Args> constexpr reference emplace_back(Args&&... args);
        constexpr void push_back(const bool& x);
        constexpr void pop_back();
        template<class... Args>
          constexpr iterator emplace(const_iterator position, Args&&... args);
        constexpr iterator insert(const_iterator position, const bool& x);
        constexpr iterator insert(const_iterator position, size_type n, const bool& x);
        template<class InputIt>
          constexpr iterator insert(const_iterator position,
                                    InputIt first, InputIt last);
        constexpr iterator insert(const_iterator position, initializer_list<bool> il);

        constexpr iterator erase(const_iterator position);
        constexpr iterator erase(const_iterator first, const_iterator last);
        constexpr void swap(vector&);
        constexpr static void swap(reference x, reference y) noexcept;
        constexpr void flip() noexcept;     // 翻转所有位
        constexpr void clear() noexcept;
      };
    }