142. 环形链表 II 我这么写为什么有个 case 无法通过

感觉也没啥区别呀

我的代码：

public class Solution {
    public ListNode detectCycle(ListNode head) {
        if(head == null || head.next == null) return null;
        ListNode fast = head;
        ListNode slow = head;
        while(fast != slow){
            if(fast == null || fast.next == null){
                return null;
            }
            slow = slow.next;
            fast = fast.next.next;
        }
        fast = head;
        while( fast != slow){
            fast = fast.next;
            slow = slow.next;
        }
        return fast;
    }
}

无法通过的 case:

输入
[3,2,0,-4]
1
输出
tail connects to node index 0
预期结果
tail connects to node index 1

可以通过的代码：

public class Solution {
    public ListNode detectCycle(ListNode head) {
        if(head == null || head.next == null) return null;
        ListNode fast = head;
        ListNode slow = head;
        while(true){
            if(fast == null || fast.next == null){
                return null;
            }
            slow = slow.next;
            fast = fast.next.next;
            if(fast == slow) break;
         }
        fast = head;
        while( fast != slow){
            fast = fast.next;
            slow = slow.next;
        }
        return fast;
    }
}