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

C++(173ms):
 1 class Solution {
 2 public:
 3     vector<vector<int>> imageSmoother(vector<vector<int>>& M) {
 4         int n = M.size() ; 
 5         int m = M[0].size();
 6         if (n == 0 || m == 0)
 7             return vector<vector<int>>() ;
 8         vector<vector<int>> dirs = {{0,1},{0,-1},{1,0},{-1,0},{-1,-1},{1,1},{-1,1},{1,-1}};
 9         vector<vector<int>> res(n) ;
10         for(int i = 0 ; i < n ; i++){
11             for (int j = 0 ; j < m ; j++){
12                 res[i].resize(m) ;
13                 int sum = M[i][j] ;
14                 int cnt = 1 ;
15                 for(int k = 0 ; k < 8 ; k++){
16                     int x = i + dirs[k][0] ;
17                     int y = j + dirs[k][1] ;
18                     if (x < 0 || x > n-1 || y < 0 || y > m-1)
19                         continue ;
20                     sum += M[x][y] ;
21                     cnt++ ;
22                 }
23                 res[i][j] = sum/cnt ;
24             }
25         }
26         return res ;
27     }
28 };

 或者   vector<vector<int>> res(n , vector<int>(m,0)) ;

posted @ 2017-10-12 09:47  __Meng  阅读(271)  评论(0编辑  收藏  举报