80. Remove Duplicates from Sorted Array II (Array)

Follow up for "Remove Duplicates":
What if duplicates are allowed at most twice?

For example,
Given sorted array nums = [1,1,1,2,2,3],

Your function should return length = 5, with the first five elements of nums being 1, 1, 2, 2 and 3. It doesn‘t matter what you leave beyond the new length.

class Solution {
public:
    int removeDuplicates(int A[], int n) {
        if(n==0) return NULL;
        int start = 0;
        for (int i = 1; i< n; i++)
        {
            if(A[start] != A[i] || ( A[start] == A[i] && i+1 < n && A[start] != A[i+1])
            || (A[start] == A[i] && i+1 >=n))
            {
                A[++start] = A[i];
            }
        }
        return start+1;
    }
};