> ## Documentation Index
> Fetch the complete documentation index at: https://leetcode-py.wisl.dev/llms.txt
> Use this file to discover all available pages before exploring further.

> ## Agent Instructions
> leetcode-py is a Python LeetCode practice environment generator with one CLI: lcpy. It is not a service or platform.
> Each problem is a directory under leetcode/ with README.md, solution.py, test_solution.py, helpers.py, and playground.ipynb. lcpy gen creates them from JSON templates bundled with the package.
> Examples are backed by tests; copy them verbatim.

# Rotate Image Python Solution with Tests

> Tested Python solution for LeetCode 48 with 12 pytest cases. Generate a practice environment with lcpy.

LeetCode 48, Medium. Topics: Array, Math, Matrix. [View on LeetCode](https://leetcode.com/problems/rotate-image/description/).

Generate this problem as a practice environment: tested reference solution, 12 [parametrized pytest cases](/practice/testing), and a playground notebook:

```bash theme={"theme":{"light":"github-light","dark":"github-dark"}}
lcpy gen -n 48   # by problem number
lcpy gen -s rotate_image   # by problem name
```

## Problem

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.

### Examples

![Example 1](https://assets.leetcode.com/uploads/2020/08/28/mat1.jpg)

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

![Example 2](https://assets.leetcode.com/uploads/2020/08/28/mat2.jpg)

```
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`

## Solution

Reference implementation from [solution.py on GitHub](https://github.com/wislertt/leetcode-py/blob/main/leetcode/rotate_image/solution.py), full suite in [test\_solution.py](https://github.com/wislertt/leetcode-py/blob/main/leetcode/rotate_image/test_solution.py):

```python theme={"theme":{"light":"github-light","dark":"github-dark"}}
class Solution:
    # Time: O(n²)
    # Space: O(1)
    def rotate(self, matrix: list[list[int]]) -> None:
        n = len(matrix)

        # Transpose matrix
        for i in range(n):
            for j in range(i, n):
                matrix[i][j], matrix[j][i] = matrix[j][i], matrix[i][j]

        # Reverse each row
        for i in range(n):
            matrix[i].reverse()
```

## Complexity

| Time  | Space |
| ----- | ----- |
| O(n²) | O(1)  |

## Tags

[Grind](/catalog/grind), [Blind 75](/catalog/blind-75), [NeetCode 150](/catalog/neetcode-150), [NeetCode 250](/catalog/neetcode-250), [NeetCode All](/catalog/neetcode), [AlgoMaster 75](/catalog/algo-master-75).