本文实例讲述了Python3实现的判断环形链表算法。分享给大家供大家参考，具体如下：
给定一个链表，判断链表中是否有环。
方案一：快慢指针遍历，若出现相等的情况，说明有环
# Definition for singly-linked list.
# class ListNode(object):
# def __init__(self, x):
# self.val = x
# self.next = None
class Solution(object):
def hasCycle(self, head):
"""
:type head: ListNode
:rtype: bool
"""
slow = fast = head
while fast and fast.next:
slow = slow.next
fast = fast.next.next
if fast == slow:
return True
return False
方案二：遍历链表，寻找.next=head的元素。 但超出时间限制
# Definition for singly-linked list.
# class ListNode(object):
# def __init__(self, x):
# self.val = x
# self.next = None
class Solution(object):
def hasCycle(self, head):
"""
:type head: ListNode
:rtype: bool
"""
if not head:
return False
cur = head.next
while cur:
if cur.next == head:
return True
cur = cur.next
return False
希望本文所述对大家Python程序设计有所帮助。
