Leetcode-Remove Duplicates from Sorted List

 1 /**
 2  * Definition for singly-linked list.
 3  * public class ListNode {
 4  *     int val;
 5  *     ListNode next;
 6  *     ListNode(int x) {
 7  *         val = x;
 8  *         next = null;
 9  *     }
10  * }
11  */
12 public class Solution {
13     public ListNode deleteDuplicates(ListNode head) {
14         if (head==null || head.next==null) return head;
15         ListNode preHead = new ListNode(-1);
16         preHead.next = head;
17         ListNode cur = head;
18         ListNode pre = preHead;
19         
20         while (cur.next!=null){
21             if (cur.val==cur.next.val){
22                 while (cur.val==cur.next.val){
23                     cur.next = cur.next.next;
24                     if (cur.next==null)
25                         break;
26                 }
27             } else {
28                 pre = cur;
29                 cur = cur.next;
30             }
31         }
32 
33         return preHead.next;           
34         
35     }
36 }