c++

class Solution {
public:
    int getDigitSum(int number) {
        int sum = 0;
        while(number) {
            sum+=number%10;
            number/=10;
        }
        return sum;
    }

    int movingCountCore(int threshold, int rows, int cols, int row, int col, vector<vector<bool> >& visit) {
        if (row < 0 || row >= rows || col < 0 || col >= cols) return 0;
        int count = 0;
        if (!visit[row][col] && getDigitSum(row)+getDigitSum(col) <= threshold) {
            visit[row][col] = true;
            ++ count;
            const int dx[4] = {-1, 0, 1, 0};
            const int dy[4] = {0, 1, 0, -1};
            for (int i = 0; i < 4; ++ i) {
                count +=  movingCountCore(threshold, rows, cols, row+dx[i], col+dy[i], visit);
            }
        }
        return count;
    }

    int movingCount(int threshold, int rows, int cols)
    {
        if (threshold <= 0 || rows <=0 || cols <= 0) return 0;
        vector<vector<bool> > visit(rows, vector<bool>(cols, false));
        return movingCountCore(threshold, rows, cols, 0, 0, visit);
    }
};