LeetCode Online Judge 题目C# 练习 - 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.

 1         public static LinkedListNode RemoveDuplicatesfromSortedListIIOpt(LinkedListNode head)

 2         {

 3             if (head == null || head.Next == null)

 4                 return head;

 5 

 6             LinkedListNode fakeHead = new LinkedListNode();

 7             LinkedListNode prev = fakeHead;

 8             prev.Next = head;

 9             LinkedListNode curr = head;

10 

11             while (curr != null && curr.Next != null)

12             {

13                 //curr Node has duplicated

14                 if ((int)curr.Value == (int)curr.Next.Value)

15                 {

16                     //find the next Node, which value != curr.value

17                     int temp = (int)curr.Value;

18                     curr = curr.Next;

19                     while (curr != null && (int)curr.Value == temp)

20                     {

21                         curr = curr.Next;

22                     }

23                     prev.Next = curr;

24                 }

25                 //curr Node has no duplicated

26                 else

27                 {

28                     prev = prev.Next;

29                     curr = curr.Next;

30                 }

31             }

32 

33             return fakeHead.Next;

34         }

代码分析：

　　这一题稍稍有点tricky。我还是创建了一个fakeNode，用来连接head，返回的时候返回fakeHead.Next, 这样下面的逻辑就适合所有的Node了，而不用去特殊处理第一个Node就有duplicate 的 corner case。

　　这种题虽然是BF，没什么好复习的，但是还是要小心再小心，不容易写出BUG FREE的CODE。