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.

// 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.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;
}
};


Java

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