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.
这里有点小trick，关于越界的问题，这里我写了一个helper来处理这个问题，看了一下其他答案，大多很繁琐，这里用函数包裹来解决越界问题是比较好的选择。
class Solution {
public int[][] imageSmoother(int[][] M) {
int col = M[0].length;
int row = M.length;
int[][] result = new int[row][col];
for(int i = 0 ;i<row;i++)
{
for(int j = 0 ;j<col;j++)
{
result[i][j]=avg(M,i,j);
}
}
return result ;
}
private int avg (int[][] M,int i ,int j )
{
int col = M[0].length;
int row = M.length;
int count = 0 ;
int sum = 0 ;
for(int k =i-1;k<=i+1;k++)
{
for(int h = j-1;h<=j+1;h++)
{
int val = helper(M,k,h);
if(val!=-1)
{
count++;
sum+=val;
}
}
}
return sum/count;
}
private int helper (int[][] M,int k,int h)
{
if(k<0||k==M.length) return -1;
if(h<0||h==M[0].length) return -1;
return M[k][h];
}
}
```.