Remove Duplicates from Sorted Array II

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

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

Your function should return length = 5, and A is now [1,1,2,2,3].

class Solution {
public:
    int removeDuplicates(int A[], int n) {
        if(n==0)
            return 0;
        int start=1;
        bool twice=false;
        for(int i=1;i<n;i++){
            if(A[i]!=A[i-1]){
                 A[start++]=A[i];
                 twice=false;
            }
            else if(!twice){
                A[start++]=A[i];
                twice=true;
            }
        }
        return start;
    }
};