题目描述：

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:

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].

题目大意：

给定二维矩阵，表示图像的灰度。对图像进行平滑处理，将每一个像素的值换成其周围9个单元格的平均值。

解题思路：

模拟题

Python代码：

class Solution(object):
    def imageSmoother(self, M):
        """
        :type M: List[List[int]]
        :rtype: List[List[int]]
        """
        dx, dy = [-1, 0, 1], [-1, 0, 1]
        w, h = len(M), len(M[0])
        N = []
        for x in range(w):
            row = []
            for y in range(h):
                nbs = [M[x + i][y + j] for i in dx for j in dy \
                       if 0 <= x + i < w and 0 <= y + j < h]
                row.append(sum(nbs) / len(nbs))
            N.append(row)
        return N

 

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