Python3实现的判断环形链表算法示例

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

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