Rotate Image

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?

解题方案：

如方阵如下所示：

1 2 3

4 5 6

7 8 9

先进行对角线对换：

1 4 7

2 5 8

3 6 9

再进行列对换：

7 4 1

8 5 2

9 6 3

代码如下：

public class RotateImage {
	public void rotate(int[][] matrix){
		//注意，下面两个的转换顺序不能颠倒
        for(int i=0;i<matrix.length;i++){	//先进行对角线对换
			for(int j=i+1;j<matrix[0].length;j++){
				int temp = 0;
				temp = matrix[i][j];
				matrix[i][j] = matrix[j][i];
				matrix[j][i] = temp;
			}
		}
		for(int i=0;i<matrix.length;i++){	//再进行行对换
			for(int j=0;j<matrix.length/2;j++){
			    int temp = 0;
			    temp = matrix[i][j];
			    matrix[i][j] = matrix[i][matrix.length-1-j];
			    matrix[i][matrix.length-1-j] = temp;
			}
		}
	}
	
}