leetcode(51)-环形链表2

# Definition for singly-linked list.
# class ListNode:
#     def __init__(self, x):
#         self.val = x
#         self.next = None

class Solution:
    def detectCycle(self, head: ListNode) -> ListNode:
        while head is not None:
            if head.val is None:
                return head
            else:
                head.val =None
                head = head.next
        return None

什么玩意