题目

https://www.nowcoder.com/practice/650474f313294468a4ded3ce0f7898b9?tpId=190&rp=1&ru=%2Factivity%2Foj&qru=%2Fta%2Fjob-code-high-rd%2Fquestion-ranking

import java.util.*;
/**
 * 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) {
        List list = new ArrayList<ListNode>();
        while(head!=null){
            if(list.contains(head)){
                return true;
            }else{
                list.add(head);
                head=head.next;
            }
        }
        return false;
    }
}