ImageSmoother661.java

/**
 * 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].
 */

public class ImageSmoother661 {
    private int[][] dirs = new int[][]{{0,0}, {0,1}, {1,1}, {1,0}, {1,-1}, {0,-1}, {-1,0}, {-1,-1}, {-1,1}};
    public int[][] imageSmoother(int[][] M) {
        int lenI = M.length;
        int lenJ = M[0].length;
        int[][] newScale = new int[lenI][lenJ];
        
        for (int i=0; i<lenI; i++) {
            for (int j=0; j<lenJ; j++) {
                int sum = 0;
                int count = 0;
                for (int[] dir: dirs) {
                    int ii = i+dir[0];
                    int jj = j+dir[1];
                    if (ii >= 0 && jj >= 0 && ii < lenI && jj < lenJ) {
                        sum += M[ii][jj];
                        count++;
                    }
                }
                newScale[i][j] = sum / count;
            }
        }
        return newScale;
    }
}