时间限制:1秒 空间限制:32768K
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?
我的代码
/**
* 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) {
//快慢指针能相遇说明有环
if((head==nullptr)||(head->next==nullptr)||
(head->next->next==nullptr))
return false;
ListNode* fast=head->next->next;
ListNode* slow=head->next;
while((fast->next)&&(fast->next->next)){
if(fast==slow)
return true;
fast=fast->next->next;
slow=slow->next;
}
return false;
}
};
运行时间:19ms
占用内存:1224k
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