[LeetCode] 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) {
if (head == null) return false;

ListNode lo = head;
ListNode hi = head;

while (hi.next != null && hi.next.next != null) {
lo = lo.next;
hi = hi.next.next;

if (lo == hi) return true;
}

return false;
}
}