题解 | #判断链表中是否有环#
判断链表中是否有环
http://www.nowcoder.com/practice/650474f313294468a4ded3ce0f7898b9
##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; } };