## 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].

## Rust Solution

``````struct Solution;

impl Solution {
fn smooth(m: &[Vec<i32>], r: usize, c: usize, h: usize, w: usize) -> i32 {
let mut sum = 0;
let mut n = 0;
if r > 0 && c > 0 {
sum += m[r - 1][c - 1];
n += 1;
}
if r > 0 {
sum += m[r - 1][c];
n += 1;
}
if r > 0 && c < w - 1 {
sum += m[r - 1][c + 1];
n += 1;
}
if c > 0 {
sum += m[r][c - 1];
n += 1;
}
sum += m[r][c];
n += 1;
if c < w - 1 {
sum += m[r][c + 1];
n += 1;
}
if r < h - 1 && c > 0 {
sum += m[r + 1][c - 1];
n += 1;
}
if r < h - 1 {
sum += m[r + 1][c];
n += 1;
}
if r < h - 1 && c < w - 1 {
sum += m[r + 1][c + 1];
n += 1;
}
sum / n
}
fn image_smoother(m: Vec<Vec<i32>>) -> Vec<Vec<i32>> {
let h = m.len();
let w = m.len();
let mut res = vec![vec![0; w]; h];
for i in 0..h {
for j in 0..w {
res[i][j] = Self::smooth(&m, i, j, h, w);
}
}
res
}
}

#[test]
fn test() {
let m: Vec<Vec<i32>> = vec_vec_i32![[1, 1, 1], [1, 0, 1], [1, 1, 1]];
let o: Vec<Vec<i32>> = vec_vec_i32![[0, 0, 0], [0, 0, 0], [0, 0, 0]];
assert_eq!(Solution::image_smoother(m), o);
}
``````

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