83. Remove Duplicates from Sorted List

 1     public ListNode deleteDuplicates(ListNode head) {
 2         if(head == null) {
 3             return null;
 4         }
 5         ListNode dummy = new ListNode(-1);
 6         dummy.next = head;
 7         while(head != null && head.next != null) {
 8             if(head.val == head.next.val) {
 9                 head.next = head.next.next;
10             } else {
11                 head = head.next;
12             }
13         }
14         return dummy.next;
15     }