Leetcode: 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].

int removeDuplicates(int A[], int n) {        // Start typing your C/C++ solution below        // DO NOT write int main() function        if(n<=2 || A==NULL)return n;int res = 1;int pre = A[0];bool twice = false;for(int i=1;i<n;i++){if(A[i]==pre && twice)continue;else if(A[i]==pre){A[res] = A[i];res++;twice=true;}else{A[res]=A[i];res++;pre = A[i];twice = false;}}return res;    }