Count number of free cell

class Solution{
  public:
  vector<long long int> countZero(int N, int K, vector<vector<int>>& arr){
      //Code Here
        long freeCells = N * N;
        std::vector<bool> filledRows(N);
        std::vector<bool> filledCols(N);
        int rowCount = 0;
        int colCount = 0;
        std::vector<long long> ans(K);
        
        for (int i = 0; i < K; i++)
        {
            int row = arr[i][0];
            int col = arr[i][1];
            
            //if it is a new row to be filledA
            if (!filledRows[row - 1])
            {
                freeCells -= (N - colCount);
                filledRows[row - 1] = true;
                rowCount++;
            }
            
            //if it is a new col to be filled
            if (!filledCols[col - 1])
            {
                freeCells -= (N - rowCount);
                filledCols[col - 1] = true;
                colCount++;
            }
            
            //remaining freeCells after filling row and col
            ans[i] = freeCells;
        }
        return ans;
  }
};