印象题
/*** Definition for singly-linked list.* class ListNode {* int val;* ListNode next;* ListNode(int x) {* val = x;* next = null;* }* }*/
public class Solution {public ListNode detectCycle(ListNode head) {ListNode fast=head,slow=head;while(true){if(fast==null||fast.next==null) return null;fast=fast.next.next;slow=slow.next;if(fast==slow)break;}fast=head;while(slow!=fast){slow=slow.next;fast=fast.next;}return fast;}
}