Given a sorted linked list, delete all duplicates such that each element appear only once.

For example,
Given 1->1->2, return 1->2.
Given 1->1->2->3->3, return 1->2->3.

含義：從已經排好序的列表中，刪除重復值節點

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

83. Remove Duplicates from Sorted List