题目

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].

答案

class Solution {
    int[][] delta = {{0,0}, {0, -1},{0, 1},{-1, 0},{1, 0},{-1,-1},{-1,1},{1,-1},{1,1}};
    public int[][] imageSmoother(int[][] M) {
        int[][] ret = new int[M.length][M[0].length];
        for(int i = 0; i < M.length; i++) {
            for(int j = 0; j < M[0].length; j++) {
                int sum = 0, num_neighbors = 0;
                for(int k = 0; k < 9; k++) {
                    int new_i = i + delta[k][0];
                    int new_j = j + delta[k][1];
                    int value = 0;
                    if(new_i >= 0 && new_i < M.length && new_j >= 0 && new_j < M[0].length) {
                        num_neighbors++;
                        value = M[new_i][new_j];                    
                    }
                    sum += value;
                }
                ret[i][j] = sum /  num_neighbors;
            }
        }
        return ret;
    }
}