leetcode-----141. 环形链表

• 链接：https://leetcode-cn.com/problems/linked-list-cycle/

代码

/*
 * @lc app=leetcode.cn id=141 lang=cpp
 *
 * [141] 环形链表
 */

// @lc code=start
/**
 * 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 || !head->next) return false;
        auto f = head->next, s = head;
        while (f) {
            s = s->next;
            f = f->next;
            if (!f) return false;
            f = f->next;
            if (s == f) return true;
        }
        return false;
    }
};
// @lc code=end