LeetCode Online Judge 题目C# 练习 - Remove Duplicates from Sorted Array

Given a sorted array, remove the duplicates in place such that each element appear only once and return the new length.

Do not allocate extra space for another array, you must do this in place with constant memory.

For example,

Given input array A = [1,1,2],

Your function should return length = 2, and A is now [1,2].

 1         public static int RemoveDuplicatesfromSortedArray(int[] A)
 2         {
 3             int prev = A[0];
 4             int numtoremove = 0;
 5             int ret = A.Length;
 6 
 7             for (int i = 1; i < ret; i++)
 8             {
 9                 if (prev == A[i])
10                 {
11                     numtoremove++;
12                 }
13                 else
14                 {
15                     if(numtoremove > 0)
16                         RemoveDuplicatesfromSortedArrayShiftLeft(A, ret, i, numtoremove);
17                     ret -= numtoremove;
18                     i -= numtoremove;
19                     numtoremove = 0;
20                     prev = A[i];
21                 }
22             }
23 
24             if (numtoremove > 0)
25             {
26                 ret -= numtoremove;
27             }
28 
29             return ret;
30         }
31 
32         public static void RemoveDuplicatesfromSortedArrayShiftLeft(int[] A, int alength, int index, int n)
33         {
34             for (int i = index; i < alength; i++)
35             {
36                 A[i - n] = A[i];
37             }
38         }

代码分析：

　　不难，用numtoremove存着几个重复的，然后remove掉（拷贝后面的上来）就可以了。

　　注意容易出错的是，ret（数组长度）要记得改，i 要记得改， prev 要记得改， numtoremove 要记得清零。

　　还有记得处理corner case, 重复的在最后一个数。