48. Rotate Image - LeetCode

class Solution:
    def rotate(self, matrix: list[list[int]]) -> None:
        """
        Do not return anything, modify matrix in-place instead.
        """
        N = len(matrix)
        for i in range(N):
            for j in range(i):
                matrix[i][j], matrix[j][i] = matrix[j][i], matrix[i][j]
        M = N // 2
        for i in range(N):
            for j in range(M):
                k = N - 1 - j
                matrix[i][j], matrix[i][k] = matrix[i][k], matrix[i][j]