题目描述:
Given a linked list, determine if it has a cycle in it.
Follow up:
Can you solve it without using extra space?
思路解析:
这个只需要快慢指针的方法就可以检测是否有环。
代码:
/** * 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) { if(head==null||head.next==null||head.next.next==null){ return false; } ListNode slow = head; ListNode fast = head.next.next; while(slow!=fast){ if(fast.next!=null&&fast.next.next!=null){ fast = fast.next.next; slow=slow.next; } else{ return false; } } return true; } }