题解 | #判断链表中是否有环#

##只有有环的情况快慢指针才会相遇

/**

• 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||head->next==NULL) return false; ListNode *pfast=head; ListNode *pslow=head; while(pfast){ pfast=pfast->next; if(!pfast) return false; if(pslow==pfast) return true; pfast=pfast->next; pslow=pslow->next; } return false; } };