A.rear%n= = front B.(front+l)%n= = rear C.rear%n -1= = front D.(rear+l)%n= = front
A.hs->next=s; B.s->next=hs; hs=s; C.s->next=hs->next;hs->next=s; D.s->next=hs; hs=hs->next;
A.top不變 B.top=0 C.top-- D.top++