A.5,4,3,2,1 B.2,1,5,4,3 C.4,3,1,2,5 D.2,3,5,4,1
A.p->next=q; q->prior=p; p->next->prior=q; q->next=q; B.p->next=q; p->next->prior=q; q->prior=p; q->next=p->next; C.q->prior=p; q->next=p->next; p->next->prior=q; p->next=q; D.q->prior=p; q->next=p->next; p->next=q; p->next->prior=q;
A.p->next->prior=p->prior; p->prior->next=p->next; B.p->next=p->next->next; p->next->prior=p; C.p->prior->next=p; p->prior=p->prior->prior; D.p->prior=p->next->next; p->next=p->prior->prior;