The range of motion of the robot

题目：
地上有一个m行n列的方格,从坐标 [0,0] 到坐标 [m-1,n-1] .一个机器人从坐标 [0, 0] 的格子开始移动,它每次可以向左、右、上、下移动一格（不能移动到方格外）,也不能进入行坐标和列坐标的数位之和大于k的格子.例如,当k为18时,机器人能够进入方格 [35, 37] ,因为3+5+3+7=18.但它不能进入方格 [35, 38],因为3+5+3+8=19.请问该机器人能够到达多少个格子？
分析：
If the robot wants to reach the bottom right corner,Just move right and down,At the same time, avoid encountering the same grid,Because there will be obstacles in the process,Moving left and moving up will go to the duplicate square,Repeated grids do not count,Therefore, it is best to use the depth-first traversal of the graph for this problem,由于k的限制,You need to create a function yourself,to calculate the grid coordinates into numbers and then with k比较,如果kLess than the sum of the function computed coordinates,那么就不能通过.

代码：

public class MovingCount {
    
    //深度优先遍历
    int m;
    int n;
    int k;
    boolean[][] visited;
    public int movingCount(int m, int n, int k) {
    
        this.m = m;
        this.n = n;
        this.k = k;
        visited = new boolean[m][n];
        return dfs(0,0);
    }

    private int dfs(int i, int j) {
    
        if (i <0 || j <0 || i >=m || j>= n || visited[i][j] || k < sum(i)+sum(j)){
    
            return 0;
        }
        visited[i][j] = true;
        return 1 + dfs(i+1,j) + dfs(i,j+1);
    }
    private int sum(int x){
    
        int res = 0;
        while (x !=0){
    
            res = res + x%10;
            x = x/10;
        }
        return res;
    }
}