LeetCode OJ 82. Remove Duplicates from Sorted List II

Given a sorted linked list, delete all nodes that have duplicate numbers, leaving only distinct numbers from the original list.

For example,
Given 1->2->3->3->4->4->5, return 1->2->5.
Given 1->1->1->2->3, return 2->3.

相对于Remove Duplicates from Sorted List这个问题，这个问题是要把重复出现过的所有元素全部删除。我的想法是找出每一个数字段的起点和终点，如果这个数据段出现了重复元素，就把这个数据段整体删除。

 public class Solution {
     public ListNode deleteDuplicates(ListNode head) {
         if(head==null || head.next==null) return head;
         ListNode thead = new ListNode(-1);
         ListNode begin = thead;
         ListNode end = head;
         thead.next = head;

         int cur = head.val;
         while(end.next!=null){
             if(end.next.val==cur){
                 end = end.next;
             }
             else{
                 if(begin.next==end){
                     begin = end;
                     end = end.next;
                 }
                 else{
                     begin.next = end.next;
                     end = begin.next;
                 }
                 cur = end.val;
             }
         }
         if(begin.next==end) return thead.next;
         begin.next = null;
         return thead.next;
     }
 }