83：删除链表中的重复元素（有序链表）

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

Example1：
Input: 1->1->2
Output: 1->2

Example2：
Input: 1->1->2->3->3
Output: 1->2->3

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