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Formatted question description: https://leetcode.ca/all/661.html

# 661. Image Smoother (Easy)

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].

Related Topics:
Array

## Solution 1.

• class Solution {
public int[][] imageSmoother(int[][] M) {
if (M == null || M.length == 0 || M[0].length == 0)
return M;
int rows = M.length, columns = M[0].length;
int[][] smooth = new int[rows][columns];
int[][] directions = { {-1, -1}, {-1, 0}, {-1, 1}, {0, 1}, {1, 1}, {1, 0}, {1, -1}, {0, -1} };
for (int i = 0; i < rows; i++) {
for (int j = 0; j < columns; j++) {
int sum = M[i][j];
int count = 1;
for (int[] direction : directions) {
int newRow = i + direction[0], newColumn = j + direction[1];
if (newRow >= 0 && newRow < rows && newColumn >= 0 && newColumn < columns) {
sum += M[newRow][newColumn];
count++;
}
}
smooth[i][j] = sum / count;
}
}
return smooth;
}
}

############

class Solution {
public int[][] imageSmoother(int[][] img) {
int m = img.length;
int n = img[0].length;
int[][] ans = new int[m][n];
for (int i = 0; i < m; ++i) {
for (int j = 0; j < n; ++j) {
int s = 0;
int cnt = 0;
for (int x = i - 1; x <= i + 1; ++x) {
for (int y = j - 1; y <= j + 1; ++y) {
if (x >= 0 && x < m && y >= 0 && y < n) {
++cnt;
s += img[x][y];
}
}
}
ans[i][j] = s / cnt;
}
}
return ans;
}
}

• // OJ: https://leetcode.com/problems/image-smoother/
// Time: O(MN)
// Space: O(1)
class Solution {
public:
vector<vector<int>> imageSmoother(vector<vector<int>>& A) {
int M = A.size(), N = A[0].size();
vector<vector<int>> ans(M, vector<int>(N));
for (int i = 0; i < M; ++i) {
for (int j = 0; j < N; ++j) {
int cnt = 0;
for (int x = i - 1; x <= i + 1; ++x) {
for (int y = j - 1; y <= j + 1; ++y) {
if (x < 0 || x >= M || y < 0 || y >= N) continue;
ans[i][j] += A[x][y];
++cnt;
}
}
ans[i][j] /= cnt;
}
}
return ans;
}
};

• class Solution:
def imageSmoother(self, img: List[List[int]]) -> List[List[int]]:
m, n = len(img), len(img[0])
ans = [[0] * n for _ in range(m)]
for i in range(m):
for j in range(n):
s = cnt = 0
for x in range(i - 1, i + 2):
for y in range(j - 1, j + 2):
if 0 <= x < m and 0 <= y < n:
cnt += 1
s += img[x][y]
ans[i][j] = s // cnt
return ans

############

class Solution(object):
def imageSmoother(self, M):
"""
:type M: List[List[int]]
:rtype: List[List[int]]
"""
m = len(M)
n = len(M[0])
ans = [[0] * n for _ in range(m)]

for i in range(m):
for j in range(n):
cnt = 0
sums = 0
for di in range(-1, 2):
for dj in range(-1, 2):
newi, newj = i + di, j + dj
if 0 <= newi < m and 0 <= newj < n:
cnt += 1
sums += M[newi][newj]
ans[i][j] = sums / cnt
return ans


• func imageSmoother(img [][]int) [][]int {
m, n := len(img), len(img[0])
ans := make([][]int, m)
for i, row := range img {
ans[i] = make([]int, n)
for j := range row {
s, cnt := 0, 0
for x := i - 1; x <= i+1; x++ {
for y := j - 1; y <= j+1; y++ {
if x >= 0 && x < m && y >= 0 && y < n {
cnt++
s += img[x][y]
}
}
}
ans[i][j] = s / cnt
}
}
return ans
}

• function imageSmoother(img: number[][]): number[][] {
const m = img.length;
const n = img[0].length;
const locations = [
[-1, -1],
[-1, 0],
[-1, 1],
[0, -1],
[0, 0],
[0, 1],
[1, -1],
[1, 0],
[1, 1],
];

const res = [];
for (let i = 0; i < m; i++) {
res.push([]);
for (let j = 0; j < n; j++) {
let sum = 0;
let count = 0;
for (const [y, x] of locations) {
if ((img[i + y] || [])[j + x] != null) {
sum += img[i + y][j + x];
count++;
}
}
res[i].push(Math.floor(sum / count));
}
}
return res;
}


• impl Solution {
pub fn image_smoother(img: Vec<Vec<i32>>) -> Vec<Vec<i32>> {
let m = img.len();
let n = img[0].len();
let locations = [
[-1, -1],
[-1, 0],
[-1, 1],
[0, -1],
[0, 0],
[0, 1],
[1, -1],
[1, 0],
[1, 1],
];

let mut res = vec![];
for i in 0..m {
res.push(vec![]);
for j in 0..n {
let mut sum = 0;
let mut count = 0;
for [y, x] in locations.iter() {
let i = i as i32 + y;
let j = j as i32 + x;
if i < 0 || i == m as i32 || j < 0 || j == n as i32 {
continue;
}
count += 1;
sum += img[i as usize][j as usize];
}
res[i].push(sum / count);
}
}
res
}
}