"""
48. Rotate Image
Difficulty: Medium
https://leetcode.com/problems/rotate-image/

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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
"""


class Solution:
    def rotate(self, matrix: List[List[int]]) -> None:
        n = len(matrix)
        for r in range(n):
            for c in range(r + 1, n):
                matrix[r][c], matrix[c][r] = matrix[c][r], matrix[r][c]

        for r in range(n):
            matrix[r].reverse()