查看链表是否有环

[题](判断链表中是否有环_牛客题霸_牛客网 (nowcoder.com))

1. 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) {
           ListNode* slow = head;
           ListNode* fast = head;
           while (fast != nullptr && fast->next != nullptr) {
               fast = fast->next->next;
               slow = slow->next;
               if (fast == slow) {
                   return true;
               }
           }
           return false;
       }
   };

2. 提示

   • 使用快慢指针，如果快指针与慢指针重合，则说明有环

3. 理解

   -

4. 问题

   -