# LeetCode 48. Rotate Image

## Description

https://leetcode.com/problems/rotate-image/

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]
]```

## Explanation

The idea would be to transpose the matrix first and then reverse each row.

## Python Solution

``````class Solution:
def rotate(self, matrix: List[List[int]]) -> None:
"""
Do not return anything, modify matrix in-place instead.
"""
for i in range(0, len(matrix)):
for j in range(i, len(matrix)):
temp = matrix[i][j]
matrix[i][j] = matrix[j][i]
matrix[j][i] = temp

for i in range(0, len(matrix)):
matrix[i] = reversed(matrix[i])``````
• Time complexity: O(N^2).
• Space complexity: O(1). since we do a rotation in place.