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

namespace std {
  template<class T, class Allocator = allocator<T>>
  class list {
  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
    list() : list(Allocator()) { }
    explicit list(const Allocator&);
    explicit list(size_type n, const Allocator& = Allocator());
    list(size_type n, const T& value, const Allocator& = Allocator());
    template<class InputIt>
      list(InputIt first, InputIt last, const Allocator& = Allocator());
    list(const list& x);
    list(list&& x);
    list(const list&, const Allocator&);
    list(list&&, const Allocator&);
    list(initializer_list<T>, const Allocator& = Allocator());
    ~list();
    list& operator=(const list& x);
    list& operator=(list&& x)
      noexcept(allocator_traits<Allocator>::is_always_equal::value);
    list& operator=(initializer_list<T>);
    template<class InputIt>
      void assign(InputIt first, InputIt last);
    void assign(size_type n, const T& t);
    void assign(initializer_list<T>);
    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;
    void      resize(size_type sz);
    void      resize(size_type sz, const T& c);
 
    // 元素访问
    reference       front();
    const_reference front() const;
    reference       back();
    const_reference back() const;
 
    // 修改器
    template<class... Args> reference emplace_front(Args&&... args);
    template<class... Args> reference emplace_back(Args&&... args);
    void push_front(const T& x);
    void push_front(T&& x);
    void pop_front();
    void push_back(const T& x);
    void push_back(T&& x);
    void pop_back();
 
    template<class... Args> iterator emplace(const_iterator position, Args&&... args);
    iterator insert(const_iterator position, const T& x);
    iterator insert(const_iterator position, T&& x);
    iterator insert(const_iterator position, size_type n, const T& x);
    template<class InputIt>
      iterator insert(const_iterator position, InputIt first, InputIt last);
    iterator insert(const_iterator position, initializer_list<T> il);
 
    iterator erase(const_iterator position);
    iterator erase(const_iterator position, const_iterator last);
    void     swap(list&) noexcept(allocator_traits<Allocator>::is_always_equal::value);
    void     clear() noexcept;
 
    // list 操作
    void splice(const_iterator position, list& x);
    void splice(const_iterator position, list&& x);
    void splice(const_iterator position, list& x, const_iterator i);
    void splice(const_iterator position, list&& x, const_iterator i);
    void splice(const_iterator position, list& x,
                const_iterator first, const_iterator last);
    void splice(const_iterator position, list&& x,
                const_iterator first, const_iterator last);
 
    size_type remove(const T& value);
    template<class Predicate> size_type remove_if(Predicate pred);
 
    size_type unique();
    template<class BinaryPredicate>
      size_type unique(BinaryPredicate binary_pred);
 
    void merge(list& x);
    void merge(list&& x);
    template<class Compare> void merge(list& x, Compare comp);
    template<class Compare> void merge(list&& x, Compare comp);
 
    void sort();
    template<class Compare> void sort(Compare comp);
 
    void reverse() noexcept;
  };
 
  template<class InputIt, class Allocator = allocator</*iter-value-type*/<InputIt>>>
    list(InputIt, InputIt, Allocator = Allocator())
      -> list</*iter-value-type*/<InputIt>, Allocator>;
 
  // 交换
  template<class T, class Allocator>
    void swap(list<T, Allocator>& x, list<T, Allocator>& y)
      noexcept(noexcept(x.swap(y)));
}