A.-1 B.0 C.不變 D.可變
A.S->top=p; B.p->next=S->top;S->top=p; C.p->next=S->top;S->top=p->next; D.p=S->top;S->top=p;
A.p=S->top;S->top=p->next; B.p=S->top;S->top=p; C.p=S;S->top=p->next; D.p=S->top;S->top=p->next->next;