用一种算法来颠倒一个链接表的顺序

Node * reverse(Node * head) {
  if (head == NULL) return head;
  if (head->next == NULL) return head;
  Node * ph = reverse(head->next);
  head->next->next = head;
  head->next = NULL;
  return ph;
}
Node * reverseNonrecurisve(Node * head) {
  if (head == NULL) return head;
  Node * p = head;
  Node * previous = NULL;
  while (p->next != NULL) {
    p->next = previous;
    previous = p;
    p = p->next;
  }
  p->next = previous;
  return p;
}