Rotate Matrix 90 degree

"""
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.
"""

class Solution:
    def rotate(self, matrix: List[List[int]]) -> None:
        """
        Do not return anything, modify matrix in-place instead.

        mat[r][c] -> mat[c][(n - 1) - r]

        => mat[r][c] <- mat[c][r] <- mat[c][(n-1)-r]
        """
        n = len(matrix)

        for r in range(len(matrix)):
            for c in range(len(matrix[0])):
                if r < c:
                    continue
                matrix[r][c], matrix[c][r] = matrix[c][r], matrix[r][c]

        for c in range(len(matrix)):
            for r in range(len(matrix)):
                if (n - 1) - r > r:
                    continue
                matrix[c][r], matrix[c][(n - 1) - r] = matrix[c][(n - 1) - r], matrix[c][r]

        return