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.

https://leetcode.com/problems/image-smoother/description/

题目要求算出每个点的附近点的平均灰度，设要求的点（i,j）附近点范围(i-1~i+1,j-1~j+1)

class Solution {public int[][] imageSmoother(int[][] M) {int[][] results = new int[M.length][M[0].length];for (int i = 0; i < M.length; i++) {for (int j = 0; j < M[0].length; j++) {int num = 0;int sum = 0;for (int k = i - 1; k <= i + 1; k++) {for (int f = j - 1; f <= j + 1; f++) {if (k >= 0 && f >= 0 && k < M.length && f < M[0].length) {num++;sum += M[k][f];}}}results[i][j] = sum / num;}}return results;}}