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;
A.a,b,c,d,e B.e,d,c,b,a C.c,b,a,d,e D.d,b,c,a,e