48. Rotate Image java solutions

 1 public class Solution {
 2     public void rotate(int[][] matrix) {
 3         int n = matrix.length;
 4         if(n == 0) return;
 5         for(int i = 0;i < n; i++){
 6             for(int j = 0;j < n-i; j++){//沿着副对角线旋转一次。
 7                 int tmp = matrix[i][j];
 8                 matrix[i][j] = matrix[n-j-1][n-i-1];
 9                 matrix[n-j-1][n-i-1] = tmp;
10             }
11         }
12         
13         for(int i = 0;i < n/2; i++){
14             for(int j = 0;j < n; j++){//沿着中轴线，上下交换一次元素
15                 int tmp = matrix[i][j];
16                 matrix[i][j] = matrix[n-i-1][j];
17                 matrix[n-i-1][j] = tmp;
18             }
19         }
20     }
21 }