题解 | #链表# #判断链表中是否有环#

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

#
# 
#
class Solution:
    def hasCycle(self , head ):
        # write code here
        ret = False 
        slow = head 
        fast = head

        while slow != None and fast != None:
            slow = slow.next
            if fast.next != None:
                fast = fast.next.next
            else:
                return False
            if slow == fast:
                return True

        return False