A.p = p->prior;p->prior->next = p->next B.p->prior->next = p;p->next = p->next->prior C.p->next->prior = p;p->next = p->next->next D.p->prior->next = p->next;p->next->prior = p->prior
A.p->next=NULL B.p->next=head C.p=NULL D.p=head
A.2n+2 B.n+1 C.n-1 D.2n-2