写正确函数需要注意的地方：链表的逆转，递归与非递归

Node* invert_list(Node* phead)
{
	if(phead==NULL || phead->pNext==NULL)//参数验证
		return phead;
	Node* p1=phead;
	Node* p2=phead->pNext;
	Node* p3=phead->pNext->pNext;

	while(p2!=NULL)
	{
		p2->pNext=p1;
		p1=p2;
		p2=p3;
		if(p3!=NULL)//到最后p3为空。因此p3->pNext时需要小心。
			p3=p3->pNext;
	}
	phead->pNext=NULL;
	return p1;
}

Node* invert_list_recu(Node* phead)
{
	if(phead==NULL || phead->pNext==NULL)
		return phead;

	Node* pnext=phead->pNext;
	Node* pheadnew=invert_list_recu(pnext);

	pnext->pNext=phead;
	return pheadnew;
}