自己造容器List

//自己造容器--List
/*
1、iterator
2、头迭代器
3、尾迭代器
4、链表长
5、判空
6、清除
7、取头元素
8、取尾元素
9、头插入
10、尾插入
11、头删除
12、尾删除
13、插入函数
14、删除函数
*/

template<typename Object>
class List
{
private:
	//结点
	struct Node
	{
		Object data;
		Node *prev;                       //前置指针
		Node *next;                     //后置指针

		Node(const Object & d = Object(), Node*p = NULL, Node*n = NULL) : data(d), prev(p), next(n){}
	};

public:
	//迭代器
	class const_iterator
	{
	public:
		const_iterator() :current(NULL){}

		//*重载
		const Object & operator*()const
		{
			return retrieve();
		}

		//pre++重载
		const_iterator & operator++()        //前置++，返回引用
		{
			current = current->next;
			return *this;        //this是一个指向iterator的指针
		}

		//pre--
		const_iterator & operator--()        //前置--，返回引用
		{
			current = current->prev;
			return *this;        //this是一个指向iterator的指针
		}

		//pos++重载
		const_iterator operator++(int)       //后置++，返回参数
		{
			const_iterator old = *this;
			++(*this);
			return old;
		}

		//pos--
		const_iterator operator--(int)       //后置--，返回参数
		{
			const_iterator old = *this;
			--(*this);
			return old;
		}

		//==重载
		bool operator==(const const_iterator & rhs)const
		{
			return current == rhs.current;
		}

		//!=重载
		bool operator!=(const const_iterator & rhs)const
		{
			return !(current == rhs.current);
		}

	protected: //在一般迭代器中变为private
		Node*current;

		Object &retrieve()const
		{
			return current->data;
		}

		const_iterator(Node*p) :current(p){}

		friend class List<Object>;
	};

	//一般迭代器继承常迭代器
	class iterator : public const_iterator
	{
	public:
		iterator(){}

		Object &operator*()
		{
			return retrieve();
		}

		//以免被上一个operator*覆盖
		const Object& operator*()const
		{
			return const_iterator::operator*();
		}

		//pre++
		iterator operator++()
		{
			current = current->next;
			return *this;
		}

		//pre--
		iterator operator--()
		{
			current = current->prev;
			return *this;
		}

		//pos++
		iterator operator++(int)
		{
			iterator old = *this;
			++(*this);
			return old;
		}

		//pos--
		iterator operator--(int)
		{
			iterator old = *this;
			--(*this);
			return old;
		}
	protected:
		iterator(Node*p) : const_iterator(p){}

		friend class List<Object>;
	};

public:
	//the big three
	List()
	{
		init();
	}

	~List()
	{
		clear();
		delete head;
		delete tail;
	}

	List(const List &rhs)
	{
		init();
		*this = rhs;
	}

	const List& operator=(const List & rhs)
	{
		if (this == &rhs)
			return *this;
		clear();
		for (const_iterator itr = rhs.begin(); itr != rhs.end(); ++itr)
			push_back(*itr);
		return *this;
	}

	//头迭代器
	iterator begin()
	{
		return iterator(head->next);
	}

	const_iterator begin()const
	{
		return const_iterator(head->next);
	}

	//尾迭代器
	iterator end()
	{
		return iterator(tail);
	}

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

	//链长
	int size()const
	{
		return theSize;
	}

	//判空
	bool empty()const
	{
		return size() == 0;
	}

	//清除
	void clear()
	{
		while (!empty())
		{
			pop_front();
		}
	}

	//取头元素
	Object & front()
	{
		return *begin();
	}

	const Object & front()const
	{
		return *begin();
	}

	//取尾元素
	Object & back()
	{
		return *--end();
	}

	const Object & back()const
	{
		return *--end();
	}

	//前插
	void push_front(const Object&x)
	{
		insert(begin(), x);
	}

	//后插
	void push_back(const Object&x)
	{
		insert(end(), x);
	}

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

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

	//插入
	iterator insert(iterator itr, const Object &x)
	{
		theSize++;
		Node *p=itr.current;
		/*Node*q=new Node(x, p->prev, p);
		p->prev->next=q;
		p->prev=q;
		return iterator(q);
		*/
		return iterator(p->prev = p->prev->next = new Node(x, p->prev, p));
	}

	//单个删除
	iterator erase(iterator itr)
	{
		Node*p = itr.current;
		iterator retVal(p->next);
		p->prev->next = p->next;
		p->next->prev = p->prev;
		delete p;
		theSize--;

		return retVal;
	}

	//多个删除
	iterator erase(iterator start, iterator end)
	{
		iterator itr;
		for (itr = start; itr != end;)
			itr = erase(itr);
		return itr;
	}

private:
	int theSize;
	Node *head;
	Node *tail;

	void init()
	{
		theSize = 0;
		head = new Node;
		tail = new Node;
		head->next = tail;
		tail->prev = head;
	}
};