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原题地址:http://oj.leetcode.com/problems/linked-list-cycle/
题意:判断链表中是否存在环路。
解题思路:快慢指针技巧,slow指针和fast指针开始同时指向头结点head,fast每次走两步,slow每次走一步。如果链表不存在环,那么fast或者fast.next会先到None。如果链表中存在环路,则由于fast指针移动的速度是slow指针移动速度的两倍,所以在进入环路以后,两个指针迟早会相遇,如果在某一时刻slow==fast,说明链表存在环路。
代码:
# Definition for singly-linked list. # class ListNode: # def __init__(self, x): # self.val = x # self.next = None class Solution: # @param head, a ListNode # @return a boolean def hasCycle(self, head): if head == None or head.next == None: return False slow = fast = head while fast and fast.next: slow = slow.next fast = fast.next.next if slow == fast: return True return False
[leetcode]Linked List Cycle @ Python,码迷,mamicode.com
[leetcode]Linked List Cycle @ Python
标签:style blog class code java javascript ext color rgb for 代码
原文地址:http://www.cnblogs.com/zuoyuan/p/3701639.html