题目:
Given a linked list, determine if it has a cycle in it.
Follow up:
Can you solve it without using extra space?
解题思路:
使用快慢指针,快指针每次走两步,慢指针每次走一步,若快指针能追上慢指针,则表明有圈。
代码如下:
/** * Definition for singly-linked list. * struct ListNode { * int val; * ListNode *next; * ListNode(int x) : val(x), next(NULL) {} * }; */ class Solution { public: bool hasCycle(ListNode *head) { if (head == NULL) { return false; } ListNode *quicker = head->next; ListNode *slower = head; while ((quicker != NULL && quicker->next != NULL) && slower != NULL && quicker != slower) { quicker = quicker->next->next; slower = slower->next; } return quicker == slower; } };
LeetCode OJ - Linked List Cycle,布布扣,bubuko.com
LeetCode OJ - Linked List Cycle
原文:http://www.cnblogs.com/dongguangqing/p/3726422.html