Rotate Image

You are given annxn2D matrix representing an image.

Rotate the image by 90 degrees (clockwise).

Follow up:
Could you do this in-place?

Tips:

如果不是in-place很好做，只要重写一遍即可。

in-place的做法是，先调换matrix[i][j] 和 matrix[j][i]，然后再调换matrix[i][j] 和 matrix[i][n - j - 1]。

需要注意的是，调换的头尾，第一次调换j从i开始，到最后结束，第二次调换j从0开始，到n/2结束。

Code:

public class Solution {
    public void rotate(int[][] matrix) {
        int m = matrix.length;
        int n = matrix[0].length;
        for (int i = 0; i < m; i++) {
            for (int j = i; j < n; j++) {
                int temp = matrix[i][j];
                matrix[i][j] = matrix[j][i];
                matrix[j][i] = temp;
            }
        }
        for (int i = 0; i < m; i++) {
            for (int j = 0; j < n / 2; j++) {
                int temp = matrix[i][j];
                matrix[i][j] = matrix[i][n - j - 1];
                matrix[i][n - j - 1] = temp;
            }
        }
    }
}