2_链表的反转

Stu * ReverseIteratively(Stu* head) {  
	
	Stu *ptr1 = head;  
	Stu *ptr2 = head->pnext;  
	while(ptr2!= NULL ){  
		Stu *ptr3 = ptr2->pnext;  
		ptr2->pnext = ptr1;  
		ptr1 = ptr2;  //实际上就等于ptr1=ptr1->pnext;
		ptr2 = ptr3;  //实际上就等于ptr2=ptr2.pnext;
	}  
	head->pnext = NULL;  
	//head->pnext->num=ptr1->num;
	head=ptr1;
	return head;  
}