48. Rotate Image

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]]
```

Example 3:

```Input: matrix = [[1]]
Output: [[1]]
```

Example 4:

```Input: matrix = [[1,2],[3,4]]
Output: [[3,1],[4,2]]
```

Constraints:

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

48. Rotate Image
``````struct Solution;

impl Solution {
fn rotate(matrix: &mut Vec<Vec<i32>>) {
matrix.reverse();
let n = matrix.len();
for i in 0..n {
for j in i + 1..n {
let a = matrix[i][j];
let b = matrix[j][i];
matrix[i][j] = b;
matrix[j][i] = a;
}
}
}
}

#[test]
fn test() {
let mut matrix: Vec<Vec<i32>> = vec_vec_i32![[1, 2, 3], [4, 5, 6], [7, 8, 9]];
let res: Vec<Vec<i32>> = vec_vec_i32![[7, 4, 1], [8, 5, 2], [9, 6, 3]];
Solution::rotate(&mut matrix);
assert_eq!(matrix, res);
}
``````