# [Solved] You are given an n x n 2D matrix representing an image, rotate the image by 90 degrees (clockwise). 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. ## Question

You are given an `n x n` 2D `matrix` representing an image, rotate the image by 90 degrees (clockwise).

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:

```Input: matrix = [[1,2,3],[4,5,6],[7,8,9]]
Output: [[7,4,1],[8,5,2],[9,6,3]]
```

Example 2:

```Input: matrix = [[5,1,9,11],[2,4,8,10],[13,3,6,7],[15,14,12,16]]
Output: [[15,13,2,5],[14,3,4,1],[12,6,8,9],[16,7,10,11]]
```

Constraints:

• `n == matrix.length == matrix[i].length`
• `1 <= n <= 20`
• `-1000 <= matrix[i][j] <= 1000`

## Python Solution

```class Solution:
def rotate(self, matrix):
"""
Do not return anything, modify matrix in-place instead.
"""
l = len(matrix)
if l==1 or l==0:
return
for i in range(l//2):
for j in range(i,l-1):
matrix[i][j],matrix[j][l-1] = matrix[j][l-1], matrix[i][j]
matrix[i][j],matrix[l-1][l-1-j+i] = matrix[l-1][l-1-j+i], matrix[i][j]
matrix[i][j],matrix[l-1-j+i][i] = matrix[l-1-j+i][i], matrix[i][j]
l-=1
return
```