# class ListNode:
#     def __init__(self, x):
#         self.val = x
#         self.next = None

#
# 
# @param head ListNode类 
# @return bool布尔型
#
class Solution:
    def hasCycle(self , head: ListNode) -> bool:
        fast = slow = head
        while fast != None and fast.next != None:
            fast = fast.next.next
            slow = slow.next
            if fast == slow:
                return 1
        return 0