/**

* 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)

return false;

ListNode stepOne = head;

ListNode stepTwo = head.next;

while (stepTwo != null) {

if (stepOne == stepTwo)

return true;

stepOne = stepOne.next;

stepTwo = stepTwo.next;

if (stepTwo == null)

break;

stepTwo = stepTwo.next;

}

return false;

}

}