机器人的运动范围

题目：

地上有一个m行和n列的方格。一个机器人从坐标0,0的格子开始移动，每一次只能向左，右，上，下四个方向移动一格，但是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。但是，它不能进入方格（35,38），因为3+5+3+8 = 19。请问该机器人能够达到多少个格子？

解答：

public class Solution {

    public static void main(String[] args) {
        int threshold = 10;
        int rows = 3;
        int cols = 7;

        System.out.println(movingCount(threshold, rows cols));
    }

    public static int movingCount(int threshold, int rows, int cols)
    {
        if(threshold < 0 || rows <= 0 || cols <= 0) {
            return 0;
        }
        
        boolean[] visited = new boolean[rows*cols];
        for(int i = 0; i < rows*cols; i++) {
            visited[i] = false;
        }
        
        int count = movingCount(threshold, rows, cols, 0, 0, visited);
        
        return count;
    }
    
    public static int movingCount(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 + movingCount(threshold, rows, cols, row+1, col, visited)+
                movingCount(threshold, rows, cols, row-1, col, visited)+
                movingCount(threshold, rows, cols, row, col+1, visited)+
                movingCount(threshold, rows, cols, row+1, col-1, visited);
        }

        return count;
    }
    
    
    public static boolean check(int threshold, int rows, int cols, int row, int col, boolean[] visited) {
        if(row >=0 && row < rows && col >= 0 && col < cols && getDigitSum(row)+getDigitSum(col) <= threshold && !visited[row*cols+col]){
            return true;
        } else {
            return false;
        }
    }
    
    
    public static int getDigitSum(int num) {
        
        int sum = 0;
        while(num > 0) {
            sum = sum + num % 10;
            num = num /10;
        }
        
        return sum;
    }
}