Remove Duplicates from Sorted List II

 1 /**
 2  * Definition for singly-linked list.
 3  * public class ListNode {
 4  *     int val;
 5  *     ListNode next;
 6  *     ListNode(int x) { val = x; }
 7  * }
 8  */
 9 public class Solution {
10     public ListNode deleteDuplicates(ListNode head) {
11         if (head == null || head.next == null) {
12             return head;
13         }
14         ListNode dummy = new ListNode(0);
15         dummy.next = head;
16         head = dummy;
17         while (head.next != null && head.next.next != null) {
18             if (head.next.val == head.next.next.val) {
19                 int val = head.next.val;
20                 while (head.next != null && head.next.val == val) {
21                     head.next = head.next.next;
22                 }
23             } else {
24                 head = head.next;
25             }
26         }
27         return dummy.next;
28     }
29 }