题解 | #判断链表中是否有环# | Python

# 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,head;
        while (fast != None and slow!=None):
            slow = slow.next;
            if (fast.next == None):
                return False;
            fast = fast.next.next;
            if (slow == fast and slow != None):
                return True;
        return False;