LeetCode: Linked List Cycle [141]
2014-09-28 16:53
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【题目】
Given a linked list, determine if it has a cycle in it.Follow up:
Can you solve it without using extra space?
【题意】
推断一个单向链表是否有环【思路】
维护两个指针p1和p2,p1每次向前移动一步,p2每次向前移动两步假设p2可以追上p1,则说明链表中存在环
【代码】
/** * 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) { ListNode*p1=head; ListNode*p2=head; while(p2){ //p1向前走一步 p1=p1->next; //p2向前走两部 p2=p2->next; if(p2)p2=p2->next; //推断p2是否追上了p1 if(p2 && p2==p1)return true; } return false; } };
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