循环双链表删除第一个值为x的结点

#include 
using namespace std;
int const NONE = 0;
int const DONE = 1; 

/* run this program using the console pauser or add your own getch, system("pause") or input loop */
class List;

//结点 
class Node{
	friend class List;
public:
	Node(double data, Node *prev = NULL, Node *next = NULL){
		this->data = data;
		this->prev = prev;
		this->next = next;
	}
private:
	double data;
	Node *prev;
	Node *next;
};

//循环双链表 
class List{
public:
	List();
	~List();
	bool isEmpty(){ return length == 0; }
	void addNode(double data);  //添加结点 
	void print();          
	void deleteX(double x);     //删除指定数值节点 
private:
	int length;
	Node *head;
	Node *end;
	Node *p;
};
List::List(){
	length = 0;
	//头结点存结点数量 
	head = new Node(0);
	end = head;
	p = NULL;
}
List::~List(){
	Node *temp = NULL;
	Node *count = head->next;
	head->next = NULL;
	while(count){
		temp = count;
		count = count->next;
		delete temp;
	}
	length = 0;
	head = NULL;
	end = NULL;
	temp = NULL;
	p = NULL;
}
//添加结点 
void List::addNode(double data){
	Node *newNode = new Node(data);
	length ++;
	head->data = length;
	if(head == end){
		end = newNode;
		head->next = newNode;
		head->prev = end;
		end->prev = head;
		end->next = head;
	}else{
		end->next = newNode;
		newNode->prev = end;
		end = newNode;
		end->next = head;
	}
	newNode = NULL;
}
void List::print(){
	Node *temp = head->next;
	if(length == 0){
		cout<<"空"<data<<'\t';
			temp = temp->next;
		}
		cout<next;
		while(p != head && p != NULL){
			if(p->data == x){
				count = DONE;
				length --;
				head->data = length;
				if(length == 0){
					head->prev = NULL;
					head->next = NULL;
					end = head;
					delete p;
					p = NULL;
				}else{
					p->next->prev = p->prev;
					p->prev->next = p->next;
					delete p;
					p = NULL;
				}
				break;
			}else{
				p = p->next;
			}
		}
		if(count == NONE){
			cout<<"未找到要删除的x值！"<>x;
	list.deleteX(x);
	list.print();
	cout<<"请输入要删除的x值："<>x;
	list.deleteX(x);
	list.print();
	cout<<"请输入要删除的x值："<>x;
	list.deleteX(x);
	list.print();
	return 0;
}