题目描述:Given a linked list, determine if it has a cycle in it.
Follow up:
Can you solve it without using extra space?
题目翻译:
给定一个链表,确定它是否有环。
进阶:
你可以不使用额外的空间解决它吗?
代码实现:
/**
* Definition for singly-linked list.
* struct ListNode {
* int val;
* ListNode *next;
* ListNode(int x) : val(x), next(NULL) {}
* };
*/
class Solution {
public:
bool hasCycle(ListNode *head) {
if(head==NULL)
return false;
ListNode* fast=head;
ListNode* slow=head;
while(fast->next!=NULL)
{
fast=fast->next->next;
if(fast==NULL)
{
return false;
}
slow=slow->next;
if(slow==fast)
{
return true;
}
}
return false;
}
};