[Leetcode]-- Remove Duplicates from Sorted List II

 1 /**
 2  * Definition for singly-linked list.
 3  * public class ListNode {
 4  *     int val;
 5  *     ListNode next;
 6  *     ListNode(int x) {
 7  *         val = x;
 8  *         next = null;
 9  *     }
10  * }
11  */
12 public class Solution {
13     public ListNode deleteDuplicates(ListNode head) {
14        if(head == null){
15         return head;
16        }
17        //在头结点之前添加safeguard，防止处理一开始就是连续节点的情况
18        ListNode safe = new ListNode(Integer.MIN_VALUE);
19        safe.next =head;
20        head = safe;
21        
22        ListNode pre = head, cur = head.next;
23        while(cur != null){
24            boolean flag = false;
25            while(cur != null && cur.next != null){
26                if(cur.val == cur.next.val){
27                    cur.next = cur.next.next;
28                    flag = true;
29                }else{
30                    break;
31                }
32            }
33            //处理剩余的一个重复节点
34            if(flag){
35                pre.next = cur.next;
36                cur = pre.next;
37                continue;
38            }
39            
40            pre = cur;
41            cur = cur.next;
42        }
43        
44        return head.next;
45     }
46 }