题解 | #牛牛队列成环#

import java.util.*;


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
        if (head == null || head.next == null)
            return false;
        ListNode slow = head;
        ListNode fast = head;
        while (fast.next.next != null) {
            slow = slow.next;
            fast = fast.next.next;
            if (slow.val == fast.val)
                return true;
        }
        return false;
    }
}