[LeetCode&Python] Problem 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:

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

3. class Solution(object):
       def imageSmoother(self, M):
           """
           :type M: List[List[int]]
           :rtype: List[List[int]]
           """
           ans=[]
           r=[]
           m=len(M)
           n=len(M[0])
           
           if (m==0 and n==0) or (m==1 and n==1):
               return M
           elif m==1:
               for j in range(n):
                   if j==0:
                       r.append((M[0][j]+M[0][j+1])//2)
                   elif j==n-1:
                       r.append((M[0][j]+M[0][j-1])//2)
                   else:
                       r.append((M[0][j]+M[0][j+1]+M[0][j-1])//3)
               ans.append(r)
               return ans
           elif n==1:
               for i in range(m):
                   if i==0:
                       r.append((M[i][0]+M[i+1][0])//2)
                       ans.append(r)
                       r=[]
                   elif i==m-1:
                       r.append((M[i][0]+M[i-1][0])//2)
                       ans.append(r)
                       r=[]
                   else:
                       r.append((M[i][0]+M[i+1][0]+M[i-1][0])//3)
                       ans.append(r)
                       r=[]
               return ans
           else:            
               for i in range(m):
                   for j in range(n):
                       if i==0:
                           if j==0:
                               r.append((M[i][j]+M[i+1][j]+M[i+1][j+1]+M[i][j+1])//4)
                           elif j==n-1:
                               r.append((M[i][j]+M[i+1][j]+M[i+1][j-1]+M[i][j-1])//4)
                           else:
                               r.append((M[i][j]+M[i+1][j]+M[i+1][j+1]+M[i][j+1]+M[i+1][j-1]+M[i][j-1])//6)
                       elif i==m-1:
                           if j==0:
                               r.append((M[i][j]+M[i-1][j]+M[i-1][j+1]+M[i][j+1])//4)
                           elif j==n-1:
                               r.append((M[i][j]+M[i-1][j]+M[i-1][j-1]+M[i][j-1])//4)
                           else:
                               r.append((M[i][j]+M[i-1][j]+M[i-1][j+1]+M[i][j+1]+M[i-1][j-1]+M[i][j-1])//6)
                       else:
                           if j==0:
                               r.append((M[i][j]+M[i][j+1]+M[i-1][j]+M[i-1][j+1]+M[i+1][j]+M[i+1][j+1])//6)
                           elif j==n-1:
                               r.append((M[i][j]+M[i][j-1]+M[i-1][j]+M[i+1][j]+M[i-1][j-1]+M[i+1][j-1])//6)
                           else:
                               r.append((M[i][j]+M[i][j-1]+M[i-1][j]+M[i+1][j]+M[i-1][j-1]+M[i+1][j-1]+M[i][j+1]+M[i-1][j+1]+M[i+1][j+1])//9)
                   ans.append(r)
                   r=[]
               return ans