指针和类的问题

#ifndef LIST_H_INCLUDED
#define LIST_H_INCLUDED
template <typename T>
struct Node
{
    Node(T &x):data(x),next(0){}
    T data;
    Node<T> *next;
};

template <typename T>
class List
{
    Node<T> *head;
public:
    List();
    void insert(T &x);
    void remove(Node<T> *p);
    bool empty();
    ~List();
};
#endif // LIST_H_INCLUDED

template <typename T>
void List<T>::insert(T &x)
{
    Node<T> *pre=head;
    while(pre->next!=0)
    {
        pre=pre->next;
    }
    Node<T> newNode=new Node<T>(x);
    pre->next=newNode;
}

#include <iostream>

using namespace std;
#include"List.h"
bool hasCycle(List<int> *link){//判断链表有没有环
    if(link==0) return false;  //用两个指针pFast和pSlow遍历链表，如果两指针相等就有环
    Node<T> *pSlow=link,*pFast=link->next;//这儿错了，但不知道怎么改
    while(pSlow!=0||pFast!=0)
    {
        if(pSlow==pFast) return true;
        pSlow=pSlow->next;
        pFast=pFast->next;
        if(pFast==0) return false;
        pFast=pFast->next;
    }
    return false;
}

int main()
{
    List<int> link;
    for(int i=0;i<9;++i) link.insert(i);
    cout<<hasCycle(link);
    return 0;
}