661. Image Smoother.md

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:

• The value in the given matrix is in the range of [0, 255].
• The length and width of the given matrix are in the range of [1, 150].

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Solution

• mine

i can't got what it mean.

• the most votes Your runtime beats 16.44 % of java submissions.

public class ImageSmoother {

    public int[][] imageSmoother(int[][] M) {
        if (M == null) return null;
        int rows = M.length;
        if (rows == 0) return new int[0][];
        int cols = M[0].length;

        int result[][] = new int[rows][cols];

        for (int row = 0; row < rows; row++) {
            for (int col = 0; col < cols; col++) {
                int count = 0;
                int sum = 0;
                for (int incR : new int[]{-1, 0, 1}) {
                    for (int incC : new int[]{-1, 0, 1}) {
                        if (isValid(row + incR, col + incC, rows, cols)) {
                            count++;
                            sum += M[row + incR][col + incC];
                        }
                    }
                }
                result[row][col] = sum / count;
            }
        }
        return result;
    }

    private boolean isValid(int x, int y, int rows, int cols) {
        return x >= 0 && x < rows && y >= 0 && y < cols;
    }
}

• Solution Your runtime beats 66.18 % of java submissions.

O(N)time O(N)space, where N is the number of pixels in our image.

class Solution {
    public int[][] imageSmoother(int[][] M) {
        int R = M.length, C = M[0].length;
        int[][] ans = new int[R][C];

        for (int r = 0; r < R; ++r)
            for (int c = 0; c < C; ++c) {
                int count = 0;
                for (int nr = r-1; nr <= r+1; ++nr){
                    for (int nc = c-1; nc <= c+1; ++nc) {
                        if (0 <= nr && nr < R && 0 <= nc && nc < C) {
                            ans[r][c] += M[nr][nc];
                            count++;
                        }
                    }
                }
                ans[r][c] /= count;
            }
        return ans;
    }
}