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

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原文链接：http://www.cnblogs.com/etcow/archive/2012/10/11/2720660.html

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#数据结构与算法

本文介绍了一种在不使用额外空间的情况下从有序数组中去除重复元素的方法，并提供了一个具体的C#实现示例。该算法通过移动数组元素来达到去除重复的目的。

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         }