单链表逆置转换有关问题，求解答。

单链表逆置转换问题，求解答。。。

C/C++ code

void LinkList<T>::Reverse( ){    if(first == NULL || first -> next == NULL)        cout << "链表为空！";    Node<T> *p1, *p2, *p3;    p1 = first;    p2 = first -> next;    p3 = NULL;    while(p2)    {        p3 = p2 -> next;        p2 -> next = p1;        p1 = p2;        p2 = p3;    }    first -> next = NULL;//此处一下感觉错误，不知道怎么弄求解答    first  -> next= p1;    while(p1)    {        cout << p1 -> data << endl;        p1 = p1 -> next;    }