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, n):
matrix[i][j], matrix[j][i] = matrix[j][i], matrix[i][j]
for j in range(n//2):
for i in range(n):
matrix[i][j], matrix[i][n-1-j] = matrix[i][n-1-j], matrix[i][j]
