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].

思路：

1 index 指向的是没有重复的递增的数组的最后一个，index后面的i, 使得A[i] != A[index], 然后index++, i++

 1 class Solution { 2 public: 3     int removeDuplicates(int A[], int n) { 4         if(n == 0) 5             return 0; 6         int index = 0; 7         for(int i = 1; i< n;i++) 8         { 9             if(A[index] != A[i])10             {11                 index++;12                 A[index] = A[i];13             }14         }15         return index + 1;16     }17 };