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:
if head==None:
return False
s=set()
s.add(head)
while head.next:
if(head.next in s):
return True
else:
s.add(head.next)
head=head.next
return False
set判重即可,你用快慢指针写也行