## Description

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

Rotate the image by 90 degrees (clockwise).

**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.

**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]
]
```

## Solutions

### 1.Reverse

```
# Time: O(n^2)
# Space: O(1)
class Solution:
def rotate(self, matrix: List[List[int]]) -> None:
"""
Do not return anything, modify matrix in-place instead.
"""
matrix.reverse()
for i in range(len(matrix)):
for j in range(i):
matrix[i][j], matrix[j][i] = matrix[j][i], matrix[i][j]
# return matrix
# 21/21 cases passed (20 ms)
# Your runtime beats 99.73 % of python3 submissions
# Your memory usage beats 100 % of python3 submissions (12.8 MB)
```

注意拓展！