Remove Duplicates from Sorted List II

描述
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.
分析
无

代码

 1 public static ListNode deleteDuplicates2(ListNode head) {
 2         if (head == null || head.next == null) 
 3             return head;
 4         
 5         int t = Integer.MIN_VALUE;
 6         ListNode fakehead = new ListNode(t);// 加了个头指针
 7         fakehead.next = head;
 8         ListNode ptr0 = fakehead;
 9         ListNode ptr1 = fakehead.next;
10         ListNode ptr2 = fakehead.next.next;
11         boolean flag = false;
12         while (ptr2 != null) {
13             if (ptr1.data == ptr2.data) {
14                 flag = true;
15                 ptr2 = ptr2.next;
16                 ptr1 = ptr1.next;
17                 if (ptr2 == null)
18                     ptr0.next = null;
19             } else {
20                 if (flag) {
21                     ptr0.next = ptr2;
22                     flag = false;
23                     ptr1 = ptr2;
24                     ptr2 = ptr2.next;
25                 } else {
26                     ptr0 = ptr0.next;
27                     ptr1 = ptr2;
28                     ptr2 = ptr2.next;
29                 }
30             }
31         }
32         return fakehead.next;
33     }