leetcode 83 Remove Duplicates from Sorted List ----- java

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.

上一道题是这道题的延伸，这个就更简单了。

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