Given a linked list, determine if it has a cycle in it.
Follow up:
Can you solve it without using extra space?
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/** * Definition for singly-linked list. * class ListNode { * int val; * ListNode next; * ListNode(int x) { * val = x; * next = null; * } * } */public
class Solution { public
boolean hasCycle(ListNode head) { boolean
hasCycle = true; if(head == null) hasCycle = false; else{ ListNode first = head; ListNode second = head; do{ if(second.next == null
|| second.next.next == null){ hasCycle = false; break; } else{ first = first.next; second = second.next; second = second.next; } }while(first != second); } return
hasCycle; }} |
原文：http://www.cnblogs.com/averillzheng/p/3545282.html