java代码

class Solution {
    static boolean[][] st = new boolean[110][110];
    static int count = 1;

    public int movingCount(int threshold, int rows, int cols)
    {
        if(rows == 0 && cols == 0) return 0;               //特判
        int res = dfs(threshold, rows, cols, 0, 0);
        return res;
    }

    private static int dfs(int k, int rows, int cols, int x, int y)
    {
        if(sum(x, y) > k) return 0;
        st[x][y] = true;
        int[] dx = {-1, 0, 1, 0}, dy = {0,1,0,-1};
        for(int i = 0; i < 4; i ++)
        {
            int a = x + dx[i], b = y + dy[i];
            if(a >= 0 && a < rows && b >= 0 && b < cols &&  sum(a, b) <= k && st[a][b] == false)
            {
                count ++;
                dfs(k, rows, cols, a, b);
            }
        }
        return count;
    }

    private static int sum(int x, int y)        //求的是数位之和
    {
        int sum = 0;
        while(x != 0)
        {
            sum += x % 10;
            x /= 10;
        }
        while(y != 0)
        {
            sum += y % 10;
            y /= 10;
        }
        return sum;
    }
}