//思路：
//flood-fill 算法
private int m;
private int n;

private boolean[][] visited;

private int[][] d={
    {0,1}, //向右
    {-1,0},//向上
    {0,-1},//向左
    {1,0} //向下
};

private boolean inArea(int x,int y){
    return (x>=0 && x<m) && (y>=0 && y<n);
}

//获取一个数各个位上的数字相加
private int getNum(int num){
    int sum = 0;
    while(num>0){
        sum += num %10;
        num/=10;
    }
    return sum;
}

private boolean valid(int threshlod ,int x,int y){
    return (getNum(x)+getNum(y))<=threshlod;
}

private int walk(int threshold,int startx,int starty){
    visited[startx][starty]=true;
    int walks = 1;
    for(int i=0;i<4;i++){
        int newX = startx+d[i][0];
        int newY = starty+d[i][1];
        if(inArea(newX,newY)){
            if(!visited[newX][newY] && valid(threshold,newX,newY)){
                walks += walk(threshold,newX,newY);
            }
        }
    }
    return walks;
}

public int movingCount(int threshold, int rows, int cols) {
    if(threshold<0){ //threshold<0，则机器人就不能走了
        return 0;
    }
    m = rows;
    if(m==0){
        return 0;
    }
    n= cols;
    visited = new boolean[m][n];
    return walk(threshold,0,0);
}