# 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 ): # write code here if not head&nbs***bsp;not head.next: return False slow, fast = head, head while fast and fast.next: slow = slow.next fast = fast.next.next if slow == fast: return True return False