leetcode-141-链表题-环形链表

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题目

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解法

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/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode(int x) : val(x), next(NULL) {}
 * };
 */

// 快慢指针
class Solution {
public:
    bool hasCycle(ListNode *head) {
        if(!head) return false;

        ListNode *slow = head;
        ListNode *fast = head->next;

        while(fast && fast->next){
            if(slow == fast) return true;
            slow = slow->next;
            fast = fast->next->next;
        }

        return false;
    }
};