Given a linked list, determine if it has a cycle in it.
Follow up:
Can you solve it without using extra space?
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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 | /** * 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 || head->next == NULL) return false; ListNode* slow = head, * fast = head; while(fast != NULL && fast->next != NULL){ slow = slow->next; fast = fast->next->next; if(slow == fast){ return true; } } return false; }}; |
原文：http://www.cnblogs.com/zhxshseu/p/4fbbbe4fd724cac6a64cda7a34a36511.html