题解 | #牛牛队列成环#

import java.util.*;
import java.util.stream.*;

/*
 * public class ListNode {
 *   int val;
 *   ListNode next = null;
 *   public ListNode(int val) {
 *     this.val = val;
 *   }
 * }
 */

public class Solution {
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     * 
     * @param head ListNode类 
     * @return bool布尔型
     */
    public boolean hasCycle (ListNode head) {
        // write code here
        List<Integer> temp = new ArrayList<>();
        while(head != null){
            temp.add(head.val);
            head = head.next;
        }

      List distinctTemp =  temp.stream().distinct().collect(Collectors.toList());
      if(temp.size() != distinctTemp.size()){
        return true;
      }else{
        return false;
      }
    }
}