题解 | #判断链表中是否有环#

/**
 * 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 *p,*q;
     p =head;
     q=head;
     while(q!=nullptr&&q->next!=nullptr)
     {
        p = p->next;
        q = q->next->next;
        if(p == q)
        {
            return true;
        }
     }
      return false;
    }
};