#pragma once
#include <iostream>
#include <list>
#include <assert.h>
using namespace std;
namespace ding
{
	//结点类
	template<class T>
	struct _list_node
	{
		_list_node(const T& val = T())
			:_data(val)
			,_next(nullptr)
			,_prev(nullptr)
		{}
		T _data;
		_list_node<T>* _next;
		_list_node<T>* _prev;
	};
	//迭代器类
	template<class T, class Ref, class Ptr>
	struct _list_iterator
	{
		typedef _list_node<T> node;
		typedef _list_iterator<T, Ref, Ptr> self;
		//构造函数
		_list_iterator(node* node)
		{
			_node = node;
		}
		self operator++()
		{
			_node = _node->_next;
			return *this;
		}
		self operator++(int)
		{
			self tmp(_node);
			_node =_node->_next;
			return tmp;
		}
		self operator--()
		{
			_node = _node->_prev;
			return *this;
		}
		
		self operator--(int)
		{
			self tmp(*this);
			_node = _node->_prev;
			return tmp;
		}
		bool operator==(const self& s) const
		{
			return _node == s._node;
		}
		bool operator!=(const self& s) const
		{
			return _node != s._node;
		}
		Ref operator*() const
		{
			return _node->_data;
		}
		Ptr operator->()
		{
			return &(_node->_data);
		}
		//成员变量
		node* _node;
	};

	//list类
	template<class T>
	class list
	{
	public:
		typedef _list_node<T> node;
		typedef _list_iterator<T, T&, T*> iterator;
		typedef _list_iterator<T, const T&, const T*> const_iterator;

		//Member functions
		void empty_init()
		{
			_head = new node;
			_head->_prev = _head;
			_head->_next = _head;
		}
		list()
		{
			empty_init();
		}
		list(const list<T>& lt)
		{
			empty_init();
			for (auto val : lt)
			{
				push_back(val);
			}
		}
		list<T>& operator=(const list<T>& lt)
		{
			if (this != &lt)//防止自己给自己赋值 自己给自己赋值都clear了数据丢失了
			{
				clear();
				for (const auto e : lt)
				{
					push_back(e);
				}
			}
			return *this;
		}
		template<class InputIterator>
		list(InputIterator first, InputIterator last)
		{
			_head = new node;
			_head->_prev = _head;
			_head->_next = _head;
			while (first != last)
			{
				push_back(*first);
				++first;
			}
		}
		~list()
		{
			clear();
			delete _head;
			_head = nullptr;
		}

		//Iterators:
		iterator begin()
		{
			return iterator(_head->_next);
		}
		iterator end()
		{
			return iterator(_head);
		}
		const_iterator begin() const
		{
			return const_iterator(_head->_next);
		}
		const_iterator end() const
		{
			return const_iterator(_head);
		}

		//Element access:
		T& front()
		{
			return *begin();
			//return _head->_next->_data;
		}
		T& back()
		{
			return _head->_prev->_data;
		}
		const T& front() const
		{
			return *begin();
		}
		const T& back() const
		{
			return *--end();
		}

		//Modifiers:
		void insert(iterator pos, const T& x)
		{
			assert(pos._node);
			node* newnode = new node(x);//创建新结点
			node* cur = pos._node;//pos位置的结点指针
			node* prev = cur->_prev;//pos前一个
			//连接关系
			prev->_next = newnode;
			newnode->_prev = prev;
			newnode->_next = cur;
			cur->_prev = newnode;
			++_size;
		}
		void push_back(const T& x)
		{
			insert(end(), x);
		}
		void push_front(const T& x)
		{
			insert(begin(), x);
		}
		iterator erase(iterator pos)
		{
			assert(pos != end());
			node* prev = pos._node->_prev;//pos位置前一个结点
			node* next = pos._node->_next;//pops位置后一个结点
			//连接关系
			prev->_next = next;
			next->_prev = prev;
			//释放删除的结点
			delete pos._node;
			--_size;
			return iterator(next);//防止迭代器失效，返回pos位置下一个迭代器
		}
		
		void pop_back()
		{
			erase(--end());
		}
		
		void pop_front()
		{
			erase(begin());
		}

		//Capacity:
		size_t size() const
		{
			return _size;
		}
		//扩容+初始化
		void resize(size_t n, const T& val = T())
		{
			size_t sz = size();
			if (sz < n)//扩容
			{
				for (; sz < n; ++sz)
				{
					push_back(val);
				}
			}
			else//不扩容
			{
				if (sz > n)//缩容
				{
					int len = sz - n;
					cout << len << endl;
					while (len--)
					{
						pop_back();
					}
				}
			}
			
		}
		void clear()
		{
			auto it = begin();
			while (it != end())
			{
				erase(it++);
			}
		}
		bool empty() const
		{
			return _head->_next;
		}
		void swap(list<T>& lt)
		{
			std::swap(_head, lt._head);
		}

	private:
		node* _head;
		size_t _size = 0;
	};

	void test_list1();
	void test_list2();
}