[LeetCode]Rotate Image/旋转图像

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

给你一个n*n表示一张图片的2维矩阵。

Rotate the image by 90 degrees (clockwise).

按照顺时针方向旋转90°。

Note:

You have to rotate the image in-place, which means you have to modify the input 2D matrix directly. DO NOT allocate another 2D matrix and do the rotation.

你只能直接利用矩阵旋转，意思是只能直接修改传入的2维矩阵，不要重新构造一个2维矩阵来进行旋转。

Example 1:

Given **input matrix**= [  
    [1,2,3],  
    [4,5,6],  
    [7,8,9]
],
rotate the input matrix **in-place** such that it becomes:
[  
    [7,4,1],  
    [8,5,2],  
    [9,6,3]
]

Example 2:

Given **input** matrix =[
  [ 5, 1, 9,11],
  [ 2, 4, 8,10],
  [13, 3, 6, 7],
  [15,14,12,16]
], 

rotate the input matrix **in-place** such that it becomes:
[
  [15,13, 2, 5],
  [14, 3, 4, 1],
  [12, 6, 8, 9],
  [16, 7,10,11]
]

解：

我们可以先按照对角线对调整个矩阵，然后再按行做对调，即可完成顺时针90°的旋转

    public static void rotate(int[][] matrix) {
        int n = matrix.length;
        //沿对角线对折，右上角变为左下角
        for(int i = 0; i