661.md

Description

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].

Solution

/**
 * @param {number[][]} M
 * @return {number[][]}
 */
var imageSmoother = function(M) {
    /** 
     * Smooth the cell
     * @param {number} i: The row number of current cell
     * @param {number} j: The column number of current cell
     */
    function smoother(i, j, origM, targetM) {
        let totalCells = 0;
        let sum = 0;
        for (let x = i-1; x <= i+1; x++) {
            for (let y = j-1; y <= j+1; y++) {
                if (x < 0 || x >= origM.length) {
                    break;
                }
                if (y >= 0 && y < origM[i].length) {
                    if (origM[x][y]) {
                        sum += origM[x][y];
                    }
                    totalCells++;
                }
            }
        }
        targetM[i][j] = Math.floor(sum/totalCells);
    }
    let result = [];
    for (let i = 0; i < M.length; i++) {
        result[i] = [];
        for (let j = 0; j < M[i].length; j++) {
            smoother(i, j, M, result);
        }
    }
    return result;
};