83. remove duplicates from sorted list

 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) { val = x; }
 * }
 */
class  {
    public ListNode deleteDuplicates(ListNode head) {
        if (head == null) return null;
        ListNode curr = head;
        while (curr != null) {
            while (curr.next != null && curr.val == curr.next.val) {
                curr.next = curr.next.next;
            }
            curr = curr.next;
        }
        return head;
    }
}