题解 | #判断链表中是否有环#

# 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:
        data = []
        p = head

        if p is None or p.next is None:
            return False

        while p!= None:
            if p not in data:
                data.append(p)
                p = p.next
            else:
                return True
        
        return False