LeetCode-141 Linked List Cycle Solution (with Java)

 1 /**
 2  * Created by sheepcore on 2019-05-14
 3  * Definition for singly-linked list.
 4  * class ListNode {
 5  *     int val;
 6  *     ListNode next;
 7  *     ListNode(int x) {
 8  *         val = x;
 9  *         next = null;
10  *     }
11  * }
12  */
13 public boolean hasCycle(ListNode head) {
14     ListNode p = head,pre = head;
15     while(p != null && p.next != null){
16         if (p.next == head) return true;
17         p = p.next;
18         pre.next = head;
19         pre = p;
20     }
21     return false;
22 }