The finger of the sword Offer 13. The range of motion of the robot

Medium difficulty 447
There is one on the ground m That's ok n Grid of columns , From coordinates [0,0] To coordinates [m-1,n-1] . A robot from coordinates [0, 0] The grid starts to move , It can go left every time 、 Right 、 On 、 Move down one space （ Can't move out of the box ）, The sum of the digits of row coordinates and column coordinates is greater than k Lattice of . for example , When k by 18 when , Robots can enter the grid [35, 37] , because 3+5+3+7=18. But it can't get into the grid [35, 38], because 3+5+3+8=19. How many squares can the robot reach ？

Example 1：
Input ：m = 2, n = 3, k = 1 Output ：3
Example 2：
Input ：m = 3, n = 1, k = 0 Output ：1

Tips ：

• 1 <= n,m <= 100
• 0 <= k <= 20

Ideas

• Walk in four directions + Discriminant conditions

Code

class Solution {
    
public:
    int split_num(int i){
    // Returns the sum of the digits of a number 
        int ix=0;
        while(i)
        {
    
            ix+=i%10;
            i/=10;
        }

        return ix;
    }
    
    vector<vector<int>> vis=vector<vector<int>>(100, vector<int>(100, 0));
    void dfs(int m,int n,int k,int i,int j){
    // Go in four directions 
        if(vis[i][j]!=0) return;
        if((split_num(i)+split_num(j))<=k)
            vis[i][j]=1;
        else
            vis[i][j]=2;
        if(vis[i][j]==1){
    
            if(i+1<m)   dfs(m,n,k,i+1,j);
            if(j+1<n)   dfs(m,n,k,i,j+1);
            if(i-1>=0)  dfs(m,n,k,i-1,j);
            if(j-1>=0)  dfs(m,n,k,i,j-1);
        }
    }
    int movingCount(int m, int n, int k) {
    
        int count=0;
        dfs(m,n,k,0,0);
        for(int i=0;i<m;i++)
        {
    
            for(int j=0;j<n;j++)
            {
    
                if(vis[i][j]==1)
                {
    
                    // printf("%d,%d\t",i,j);
                    count++;
                }
            }
            // printf("\n");
        }
        return count;
    }
};