141. Linked List Cycle

• Total Accepted: 158161
• Total Submissions: 443008
• Difficulty: Easy
• Contributors: Admin

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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来源： https://leetcode.com/problems/linked-list-cycle/

分析

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见LintCode Cycle I 和 II

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/**  * 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;     } };

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