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

代码如下：

 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 heads=head;
15         ListNode p=head.next;
16         while(p!=null)
17         {
18             if(p.val==heads.val)
19             {
20                 p=p.next;
21                 heads.next=p;
22             }
23             else
24             heads=heads.next;
25         }
26         return head;
27     }
28 }