Remove Duplicates from Sorted List

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) {
 *         val = x;
 *         next = null;
 *     }
 * }
 */
public class Solution {
   public ListNode deleteDuplicates(ListNode head) {
        ListNode sorted , unsorted;//在sorted之前的所有结点中元素都不会重复，unsorted之后的结点还没有判断，在sorted之前的结点是否有重复的元素
        if(head != null){
            sorted = head;
            unsorted = sorted.next;
            while(unsorted != null){
                ListNode p  = head ;
                while(p.val != unsorted.val){
                    p = p.next;
                }
                
                if(p != unsorted){
                    sorted.next = unsorted.next;
                }
                else{
                    sorted =unsorted;
                }
                unsorted = sorted.next;
            }
            return head;
        }
        return head;
    }
}