Rotate Image leetcode java

題目：

You are given an n x n 2D matrix representing an image.

Rotate the image by 90 degrees (clockwise).

Follow up:
Could you do this in-place?

 

題解：

這道題就是考察很直白的旋轉座標。要in place的。畫個圖自己算算就出來了。

程式碼如下：

 

 1  /*   public void rotate(int[][] matrix) {
 2         int m = matrix.length;
 3         int n = matrix[0].length;
 4         
 5         int[][] result = new int[m][n];
 6         
 7         for(int i = 0; i<m; i++){
 8             for(int j = 0; j<n; j++){
 9                 result[j][m-1-i] = matrix[i][j];
10             }
11         }
12         
13         for(int i=0;i<m;i++){
14             for(int j=0; j<n; j++){
15                  matrix[i][j] = result[i][j];
16             }
17         }
18     }
19     */
20     
21     //in place
22     public void rotate(int[][] matrix) {
23     int n = matrix.length;
24     for (int i = 0; i < n / 2; i++) {
25         for (int j = 0; j < Math.ceil(((double) n) / 2.); j++) {
26             int temp = matrix[i][j];
27             matrix[i][j] = matrix[n-1-j][i];
28             matrix[n-1-j][i] = matrix[n-1-i][n-1-j];
29             matrix[n-1-i][n-1-j] = matrix[j][n-1-i];
30             matrix[j][n-1-i] = temp;
31         }
32     }