链表高级算法——2

int CheckCross(pLinkList list1, pLinkList list2)   //判断链表是否相交
{
	assert(list1);
	assert(list2);
	pLinkNode cur1 = list1->pHead;
	pLinkNode cur2 = list2->pHead;
	if ((NULL==list1->pHead)||(NULL==list2->pHead))
	{
		return -1;
	}
	while (NULL!=cur1->next)
	{
		cur1 = cur1->next;
	}
	while(NULL!=cur2->next)
	{
		cur2 = cur2->next;
	}
	if (cur1 == cur2)
	{
		return  1;                //相交
	}
	else
	{
		return -1;                 //不相交
	}
}

pLinkList Merge(pLinkList list1, pLinkList list2)    //合并两个有序链表
{
	assert(list1);
	assert(list2);
	if ((NULL == list1->pHead)&&(NULL == list2->pHead))   //考虑特殊情况
	{
		return NULL;
	}
	else if (NULL == list1->pHead)
	{
		return list2;
	}
	else if(NULL == list2->pHead)
	{
		return list1;
	}
	pLinkNode last = NULL;
	pLinkNode newHead = NULL;                       //虚拟头结点
	if (list1->pHead->data <list2->pHead->data)     //把对第一个结点特殊处理
	{
		newHead= list1->pHead;
		list1->pHead = list1->pHead->next;
	}
	else
	{
		newHead = list2->pHead;
		list2->pHead = list2->pHead->next;
	}
	last=newHead;                                    //让last指向虚拟结点链表的尾部
	while ((NULL!= list1->pHead)&&(NULL!= list2->pHead))
	{ 
		if (list1->pHead->data <list2->pHead->data)
		{
			last->next = list1->pHead;
			list1->pHead = list1->pHead->next;
		}
		else
		{
			last ->next= list2->pHead;
			list2->pHead = list2->pHead->next;
		}
		last = last->next;
	}
	if (NULL == list1->pHead)                 //将集合中剩下的元素链接到last之后
	{
		last->next = list2->pHead;
	}
	else
	{
		last->next = list1->pHead;
	}
	list1->pHead = newHead;
	return list1;
}

pLinkNode CheckCycle(pLinkList list)             //判断是否带环,若带环则返回相遇位置
{
	assert(list);
	pLinkNode fast = list->pHead;                 //快指针
	pLinkNode slow = list->pHead;                 //慢指针
	if (NULL==list->pHead)
	{
		return NULL;
	}
	while (fast!= NULL)
	{
		if (NULL != fast->next)
		{
			fast = fast->next->next;
			slow = slow->next;
		}
		else
		{
			break;
		}
		if (fast == slow)                   //快慢指针相遇则有环
		{ 
			return slow;
		}
	}
	return NULL;                            //没环则返回NULL
}

int  GetCircleLength(pLinkNode meet)         //若链表带环这返回环的长度
{
	assert(meet);
	pLinkNode cur = meet->next;
	int count = 1;
	while (cur!=meet)
	{
		count++;
		cur = cur->next;
	}
	return count;
}