C++学习：list模拟实现

一：结点

这次结构有点多但并不复杂

template<class T>
	struct list_node
	{
		T _data;
		list_node<T>* _next;
		list_node<T>* _prev;

		list_node(const T& x = T())
			:_data(x)
			,_next(nullptr)
			,_prev(nullptr)
		{}
	};

二：迭代器

别看传了三个参数，其实就是T T& T* 你就只想传一个也可以咱只是为了让两种迭代器能用一套代码而已。

    // T T& T* 
	// T cosnt T& const 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)
		{}

		self& operator++()
		{
			_node = _node->_next;
			return *this;
		}

		self& operator--()
		{
			_node = _node->_prev;
			return *this;
		}

		self operator++(int)
		{
			self tmp(*this);
			_node = _node->_next;

			return tmp;
		}

		self operator--(int)
		{
			self tmp(*this);
			_node = _node->_prev;

			return tmp;
		}

		Ref operator*()
		{
			return _node->_data;
		}

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

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

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

三：list

这里就没啥好说了和链表差不多的最后和上面的都包到你的命名空间里就行

template<class T>
	class list
	{
		typedef list_node<T> Node;
	public:
		typedef __list_iterator<T, T&, T*> iterator;
		typedef __list_iterator<T, const T&, const T*> const_iterator;

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

		const_iterator end() const
		{
			return const_iterator(_head);
		}

		iterator begin()
		{
			//return iterator(_head->_next);
			return _head->_next;//隐私类型转换
		}

		iterator end()
		{
			//return iterator(_head->_next);
			return _head;
		}

		void empty_init()
		{
			_head = new Node;
			_head->_next = _head;
			_head->_prev = _head;

			_size = 0;
		}

		list()
		{
			empty_init();
		}

		list(const list<T>& lt)
		{
			empty_init();
			for (auto e : lt)
			{
				push_back(e);
			}
		}

		
		

		void swap(list<T>& lt)
		{
			std::swap(_head, lt._head);
			std::swap(_size, lt._size);
		}

		
		list<int>& operator=(list<int> lt)
		{
			swap(lt);

			return *this;
		}

		~list()
		{
			clear();

			delete _head;
			_head = nullptr;
		}

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

		void push_back(const T& x)
		{
			insert(end(), x);
		}

		void push_front(const T& x)
		{
			insert(begin(), x);
		}

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

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

		iterator insert(iterator pos, const T& x)
		{
			Node* cur = pos._node;
			Node* newnode = new Node(x);

			Node* prev = cur->_prev;

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

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

			++_size;

			return iterator(newnode);
		}

		iterator erase(iterator pos)
		{
			Node* cur = pos._node;
			Node* prev = cur->_prev;
			Node* next = cur->_next;

			delete cur;
			prev->_next = next;
			next->_prev = prev;

			--_size;

			return iterator(next);
		}

		size_t size()
		{
			return _size;
		}

	private:
		Node* _head;
		size_t _size;
	};