Linked List Cycle

1/**
2 * Definition for singly-linked list.
3 * class ListNode {
4 *     int val;
5 *     ListNode next;
6 *     ListNode(int x) {
7 *         val = x;
8 *         next = null;
9 *     }
10 * }
11 */
12public class Solution {
13    public boolean hasCycle(ListNode head) {
14        ListNode slow = head;
15        ListNode fast = head;
16
17        while (fast != null && fast.next != null) {
18            fast = fast.next.next;
19            if (fast == slow) {
20                return true;
21            }
22            slow = slow.next;
23        }
24
25        return false;
26    }
27}