[C++知识库]C++：list的模拟实现

list的模拟实现

#include <iostream>
#include <assert.h>
using namespace std;

//按需实例化
namespace MyList
{
	//结点 内部使用加__
	//__list_node类名，__list_node<T>类型
	template<class T>
	struct __list_node
	{
		T _data;
		__list_node<T>* _next;
		__list_node<T>* _prev;

		//new node的构造
		__list_node(const T& x = T())
			: _data(x)
			, _next(nullptr)
			, _prev(nullptr)
		{}
	};

	//<T, T&, T*>
	//
	//
	template<class T, class Ref, class Ptr>
	struct __list_iterator
	{
		typedef __list_node<T> node;
		typedef __list_iterator<T, Ref, Ptr> self;
		node* _node;

		__list_iterator(node* node)
			: _node(node)
		{}

		//拷贝构造 赋值重载 析构都不用实现，默认就可以

		bool operator!=(const self& s) const
		{
			return _node != s._node;
		}

		bool operator==(const self& s) const
		{
			return _node == s._node;
		}

		Ptr operator->() const
		{
			return &(_node->_data);
		}

		//_data是T类型
		Ref operator*() const
		{
			return _node->_data;
		}

		// ++it
		self& operator++() 
		{
			_node = _node->_next;

			return *this;
		}

		//it++
		self operator++(int)
		{
			self ret(*this);
			_node = _node->_next;
			return ret;
		}

		// --it
		self& operator--()
		{
			_node = _node->_prev;

			return *this;
		}

		//it--
		self operator--(int)
		{
			self ret(*this);
			_node = _node->_prev;
			return ret;
		}
	};

	//链表
	template<class T>
	class list
	{
		//重命名
		typedef __list_node<T> node;
	public:
		typedef __list_iterator<T, T&, T*> iterator;
		typedef __list_iterator<T, const T&, const T*> const_iterator;


		iterator begin()
		{
			return _head->_next;
			//return iterator(_head->_next)

			//iterator it(_head->_next);
			//return it;
		}

		//反向迭代器，适配器模式完成
		iterator end()
		{
			return _head;
		}

		const_iterator begin() const
		{
			return _head->_next;
		}

		const_iterator end() const
		{
			return _head->_prev;
		}

		list()
		{
			_head = new node();
			_head->_next = _head;
			_head->_prev = _head;
		}

		list(const list<T>& lt)
		{
			_head = new node();
			_head->_next = _head;
			_head->_prev = _head;

			list<T> tmp(lt.begin(), lt.end());
			std::swap(_head, tmp._head);
		}

		template<class InputIterator>
		list(InputIterator first, InputIterator last)
		{
			_head = new node();
			_head->_next = _head;
			_head->_prev = _head;

			while (first != last)
			{
				push_back(++first);

			}
		}

		list<T>& operator=(list<T> lt)
		{
			std::swap(_head, lt._head);
			return *this;
		}

		~list()
		{
			clear();
			delete _head;
			_head = nullptr;
		}

		void clear()
		{
			iterator it = begin();
			while (it != end())
			{
				erase(it++);
			}
		}

		void push_back(const T& x)
		{
			node* newnode = new node(x);
			node* tail = _head->_prev;

			tail->_next = newnode;
			newnode->_prev = tail;
			newnode->_next = _head;
			_head->_prev = newnode;

			//insert(end(), x);
		}

		void push_front()
		{
			insert(begin(), x);
		}

		void pop_back()
		{
			erase(--end());
		}

		void pop_front()
		{
			erase(begin());
		}

		iterator insert(iterator pos, const T& x)
		{
			node* newnode = new node(x);
			node* cur = pos._node;
			node* prev = cur->_prev;

			prev->_next = newnode;
			newnode->_prev = prev;
			newnode->_next = cur;
			cur->_prev = newnode;

			return newnode;
		}

		iterator erase(iterator pos)
		{
			assert(pos != end());

			node* cur = pos._node;
			node* prev = cur->_prev;
			node* next = cur->_next;
			prev->_next = cur->_next;
			cur->_next->_prev = prev;

			delete cur;
			return next;
		}



	private:
		//双向带头循环
		node* _head;

	};

}