循环链表

<span style="font-size:18px;">#include<iostream>
using namespace std;
typedef int DataType;
class LinkNode
{
	friend class Slist;
public:
	LinkNode(const DataType& x)
		:_date(x)
		, _prev(NULL)
		, _next(NULL)
	{
	}
public:
	DataType _date;
	LinkNode* _prev;
	LinkNode* _next;

};
class Slist
{
public:
	Slist()
		:_head(NULL)
		, _tail(NULL)
	{}
	~Slist()
	{}
	Slist(const Slist& s)
	{}
	Slist operator=(const Slist& s)
	{}
public:
	void Print()//打印
	{
		LinkNode* begin = _head;
		while (begin)
		{
			cout << begin->_date << "->";
			begin = begin->_next;
		}
		cout << "NULL" << endl;
	}
	void PushBack(const DataType& x)//尾插
	{
		//1.链表为空
		if (_head == NULL)
		{
			_head = new LinkNode(x);
			_tail = _head;
		}
		//2.有两个以上节点
		else
		{
			LinkNode* tmp = new LinkNode(x);
			_tail->_next = tmp;
			tmp->_prev = _tail;
			_tail = tmp;
		}
	}
	void PopBack()//尾删
	{
		//1.链表为空
		if (_head == NULL)
		{
			cout << "链表为空!" << endl;
			return;
		}
		//2.只有一个节点
		else if (_head == _tail)
		{
			delete _head;
			_head = NULL;
			_tail = NULL;
		}
		//3.有两个以上节点
		else
		{
			LinkNode* del = _tail;
			_tail = _tail->_prev;
			delete del;
			_tail->_next = NULL;
		}
	}
	void PushFront(const DataType& x)//头插
	{
		//1.链表为空
		if (_head == NULL)
		{
			_head = new LinkNode(x);
			_tail=_head;
		}
		//2.有两个以上节点
		else
		{
			LinkNode *tmp = new LinkNode(x);
			tmp->_next = _head;
			_head->_prev = tmp;
			_head = tmp;
		}
	}
	void PopFront()//头删
	{
		//1.链表为空
		if (_head == NULL)
		{
			cout << "链表为空!" << endl;
			return;
		}
		//2.只有一个节点
		else if (_head == _tail)
		{
			delete _head;
			_head = NULL;
			_tail = NULL;
		}
		//3.有两个以上节点
		else
		{
			LinkNode* del = _head;
			_head = _head->_next;
			delete del;
			_head->_prev = NULL;
		}
	}
	LinkNode* Find(const DataType& x)//查找
	{
		//1.链表为空
		if (_head == NULL)
		{
			return NULL;
		}
		//2.链表不为空
		else
		{
			LinkNode* begin = _head;
			while (begin!= NULL)
			{
				if (begin->_date == x)
				{
					return begin;
				}
				begin = begin->_next;
			}
			return NULL;
		}
	}
	void Insert(LinkNode* pos, const DataType& x)//pos后面插入节点
	{
		//1.链表为空
		if (_head == NULL)
		{
			_head = new LinkNode(x);
			_tail = _head;
		}
		//2.有两个以上节点
		else if (pos==_tail)
		{
			PushBack(x);
		}
		else
		{
			LinkNode* tmp = new LinkNode(x);
			tmp->_next = pos->_next;
			pos->_next->_prev = tmp;
			pos->_next = tmp;
			tmp->_prev = pos;
		}
	}
	void Erase(LinkNode* del)//删除节点
	{
		//1.链表为空
		if (_head == NULL)
		{
			cout << "链表为空!" << endl;
			return;
		}
		//2.只有一个节点
		else if (_head == _tail)
		{
			if (_head == del)
			{
				delete _head;
				_head = NULL;
				_tail = NULL;
			}
			else
			{
				return;
			}
		}
		//两个以上节点
		else
		{
			if (_head == del)
			{
				_head = _head->_next;
				_head->_prev = NULL;
			}
			else if (del == _tail)
			{
				_tail = _tail->_prev;
				_tail->_next = NULL;
			}
			else
			{
				LinkNode* prev = del->_prev;
				LinkNode* next = del->_next;
				prev->_next = next;
				next->_prev = prev;
			}
			delete del;
		}
	}
	void Reverse()//逆置
	{
		LinkNode* begin = _head;
		LinkNode* last = _tail;
		if (_head == _tail)
		{
			return;
		}
		else
		{
			//while(begin!=last && last->next!=begin)
			while (begin!=last)
			{
				if (last->_next == begin)
				{
					return;
				}
				swap(begin->_date, last->_date);
				begin = begin->_next;
				last = last->_prev;
			}
		}

	}
private:
	LinkNode* _head;
	LinkNode* _tail;
}; 
void Test1()
{
	Slist s1;
	s1.PushBack(1);
	s1.PushBack(2);
	s1.PushBack(3);
	s1.PushBack(4);
	s1.Print();
	s1.PopBack();
	s1.Print();
	s1.PopBack();
	s1.Print();
	s1.PopBack();
	s1.Print();
	s1.PopBack();
	s1.Print();
}
void Test2()
{
	Slist s2;
	s2.PushFront(1);
	s2.PushFront(2);
	s2.PushFront(3);
	s2.PushFront(4);
	s2.Print();
	s2.PopFront();
	s2.Print();
	s2.PopFront();
	s2.Print();
	s2.PopFront();
	s2.Print();
	s2.PopFront();
	s2.Print();
	s2.PopFront();
}
void Test3()
{
	Slist s3;
	s3.PushBack(1);
	s3.PushBack(2);
	s3.PushBack(3);
	s3.PushBack(4);
	s3.Print();
	LinkNode* ret1 = s3.Find(1);
	cout << ret1->_date << endl;
	LinkNode* ret2 = s3.Find(3);
	cout << ret2->_date << endl;
	LinkNode* ret3 = s3.Find(4);
	cout << ret3->_date << endl;
	LinkNode* ret4 = s3.Find(5);
	cout << ret4 << endl;
}
void Test4()
{
	Slist s3;
	s3.PushBack(1);
	s3.PushBack(2);
	s3.PushBack(3);
	s3.PushBack(4);
	s3.Print();
	LinkNode* ret1 = s3.Find(1);
	s3.Insert(ret1, 5);
	s3.Print();
	LinkNode* ret2 = s3.Find(2);
	s3.Insert(ret2, 7);
	s3.Print();
	LinkNode* ret3 = s3.Find(4);
	s3.Insert(ret3, 8);
	s3.Print();
}
void Test5()
{
	Slist s5;
	s5.PushBack(1);
	s5.PushBack(2);
	s5.PushBack(3);
	s5.PushBack(4);
	//s5.PushBack(5);
	s5.Print();
	s5.Reverse();
	s5.Print();
}
int main()
{
	//Test1();
	//Test2();
	//Test3();
	//Test4();
	Test5();
	return 0;
}</span>