使用快慢指针就好啦
/**
* Definition for singly-linked list.
* class ListNode {
* int val;
* ListNode next;
* ListNode(int x) {
* val = x;
* next = null;
* }
* }
*/
public class Solution {
public boolean hasCycle(ListNode head) {
if(head==null||head.next==null) return false;
ListNode fast = head.next ;
ListNode slow = head ;
while(fast!=slow)
{
if(fast!=null&&fast.next!=null)
fast=fast.next.next;
else
return false;
if(slow!=null)
slow=slow.next;
else
return false;
}
return true;
}
}
