A.s->next=p->next;p->next=s; B.p->next=s;s->next=p->next; C.s->next=p;p->next=s->next; D.p->next=s;s->next=p;
A.O(0) B.O(1) C.O(n) D.O(n2)
A.n-i B.n-i+1 C.i D.n-i-1