机器人的运动范围（Java实现）

public class E13RobotMovingRange {
    //机器人从坐标（0，0）开始运动，计算坐标位数不大于k的可到达格数

    public static int getMovingCount(int threshold, int rows, int cols) {
        if (threshold < 0 || rows <= 0 || cols <= 0)
            return 0;
        //避免重复计算
        boolean[] visited = new boolean[rows * cols];

        return count(threshold, rows, cols, 0, 0, visited);
    }

    //计算可到达格数
    private static int count(int threshold, int rows, int cols,
                             int row, int col, boolean[] visited) {
        int count = 0;
        if (check(threshold, rows, cols, row, col, visited)) {
            visited[row * cols + col] = true;
            count = 1 + count(threshold, rows, cols, row + 1, col, visited) +
                    count(threshold, rows, cols, row - 1, col, visited) +
                    count(threshold, rows, cols, row, col + 1, visited) +
                    count(threshold, rows, cols, row, col - 1, visited);
        }
        return count;
    }

    //判断某坐标是否可到达
    private static boolean check(int threshold, int rows,
                                 int cols, int row, int col, boolean[] visited) {
        return row >= 0 && row < rows && col >= 0 && col < cols &&
                checkCount(col) + checkCount(row) <= threshold && !visited[row * cols + col];
    }

    //计算某数字位数之和
    private static int checkCount(int number) {
        int count = 0;
        while (number > 0) {
            count += number % 10;
            number /= 10;
        }
        return count;
    }

    //测试用例
    public static void main(String[] args){
        int count = E13RobotMovingRange.getMovingCount(2, 3, 3);
        System.out.println(count);
        /*
        * 00 01 02
        * 10 11 12
        * 20 21 22
        */
    }
}