【LeetCode OJ】Linked List Cycle

/**
* 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) {
ListNode step1 = head;
ListNode step2 = head;
if(head == null || head.next == null)return false;
while(step1 != null && step2 != null && step2.next != null){
step1 = step1.next;
step2 = step2.next.next;
if(step1 == step2){
return true;
}
}
return false;
}
}