判断链表是否有环:链表反转
判断链表中是否有环
http://www.nowcoder.com/questionTerminal/650474f313294468a4ded3ce0f7898b9
链表反转,如果有环的话最终还会反转到头节点
class Solution { public: bool hasCycle(ListNode *head) { //fanzhan if(head==NULL){ return false; } if(head->next==NULL){ return false; } ListNode * p1=head; ListNode * p2=head->next; ListNode * p3=head->next->next; while(p3){ if(p2==head){ return true; } p2->next=p1; p1=p2; p2=p3; p3=p3->next; } return false; } };