LeetCode 661. Image Smoother

Given a 2D integer matrix M representing the gray scale of an image, you need to design a smoother to make the gray scale of each cell becomes the average gray scale (rounding down) of all the 8 surrounding cells and itself. If a cell has less than 8 surrounding cells, then use as many as you can.

Example 1:

Input:
[[1,1,1],
 [1,0,1],
 [1,1,1]]
Output:
[[0, 0, 0],
 [0, 0, 0],
 [0, 0, 0]]
Explanation:
For the point (0,0), (0,2), (2,0), (2,2): floor(3/4) = floor(0.75) = 0
For the point (0,1), (1,0), (1,2), (2,1): floor(5/6) = floor(0.83333333) = 0
For the point (1,1): floor(8/9) = floor(0.88888889) = 0

Note:

• The value in the given matrix is in the range of [0, 255].
• The length and width of the given matrix are in the range of [1, 150].

class Solution {
public:
    bool islegal(int i, int j){
        if(i>=0&&i<row&&j>=0&&j<col)
           return true;
        else
           return false;
    }
    vector<vector<int>> imageSmoother(vector<vector<int>>& M) {
         vector<vector<int>> temp=M;
         row=M.size(), col=M[0].size();
         for(int i=0; i<row; i++)
             for(int j=0; j<col; j++){
                 double cnt=0,sum=0;
                 for(int k=0;k<9;k++){
                     int r=i+dict[k][0], c=j+dict[k][1];
                     if(islegal(r,c)){
                         cnt++;
                         sum+=M[r][c];
                     }
                 }
                 temp[i][j]=floor(sum/cnt);
             }
        return temp;
    }
private:
    int row, col;
    vector<vector<int>> dict={{1,0},{0,1},{1,1},{0,0},{-1,0},{0,-1},{-1,-1},{1,-1},{-1,1}};
};