在双向链表中，删除指针p所指向的结点时需要的操作是
p->next->prior=p->prior; p->prior->next=p->next
p->next=p->next->next; p->next->prior=p
p->prior->next=p; p->prior=p->prior->prior
p->prior=p->next->next; p->next=p->prior->prior
