LeetCode -- Linked List Cycle

题目链接

题意: 给出单链表, 判断是否存在环.

方法就是大步小步...

附上代码:

/**
 * 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) {
        if (head == NULL or head->next == NULL) {
            return false;
        }
        ListNode *fast = head, *slow = head;
        while (fast != NULL and fast->next != NULL) {
            fast = fast->next;
            if (fast == slow) {
                return true;
            }
            fast = fast->next;
            if (fast == slow) { 
                return true;
            }
            slow = slow->next;
        }
        return false;
    }
};