# Leetcode Rotate-Image

2022-09-02 15:40

> ##### Algorithms:
> #algorithm #math
> ##### Data structures:
> #DS #array 
> ##### Difficulty:
> #coding_problem #difficulty-medium 
> ##### Additional tags:
> #leetcode #CS_list_need_understanding
> ##### Revisions:
> N/A

##### Links:
- [Link to problem](https://leetcode.com/problems/rotate-image/)
- [Solution and explanation](https://leetcode.com/problems/rotate-image/solution/)
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### 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**](https://en.wikipedia.org/wiki/In-place_algorithm), 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

### Thoughts

> [!summary]
> This is a #math problem.

Mainly two ways

#### Method 1: rotate in rings

#### Method 2: transpose and reflect

### Solution