0661-image-smoother.js

/**
 * 661. Image Smoother
 * https://leetcode.com/problems/image-smoother/
 * Difficulty: Easy
 *
 * An image smoother is a filter of the size 3 x 3 that can be applied to each cell of an image by
 * rounding down the average of the cell and the eight surrounding cells (i.e., the average of the
 * nine cells in the blue smoother). If one or more of the surrounding cells of a cell is not
 * present, we do not consider it in the average (i.e., the average of the four cells in the red
 * smoother).
 *
 * Given an m x n integer matrix img representing the grayscale of an image, return the image after
 * applying the smoother on each cell of it.
 */

/**
 * @param {number[][]} img
 * @return {number[][]}
 */
var imageSmoother = function(img) {
  const result = new Array(img.length).fill().map(() => {
    return new Array(img[0].length).fill(0);
  });

  for (let i = 0; i < img.length; i++) {
    for (let j = 0; j < img[0].length; j++) {
      let sum = 0;
      let count = 0;
      for (let di = -1; di <= 1; di++) {
        for (let dj = -1; dj <= 1; dj++) {
          const ni = i + di;
          const nj = j + dj;
          if (ni >= 0 && ni < img.length && nj >= 0 && nj < img[0].length) {
            sum += img[ni][nj];
            count++;
          }
        }
      }
      result[i][j] = Math.floor(sum / count);
    }
  }

  return result;
};