[LeetCode] 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].

用两根指针分别扫描，一个记录当前的新数组长度，一个从前往后扫描数组，由于排序过，所以记录每次新出现的数，发现一个数和当前数不一样了，则做更新。O(n)

class Solution {
public:
    int removeDuplicates(int A[], int n) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        if (n == 0)
            return 0;
            
        int start = 0;
        int key = A[0];
        for(int i = 0; i < n; i++)
            if (A[i] != key)
            {
                A[start++] = key;
                key = A[i];                
            }
            
        A[start++] = key;
        
        return start;
    }
};