"""

Rotate Image

Rotate an n x n 2D matrix representing an image by 90 degrees clockwise,

in-place. First reverse the rows top-to-bottom, then transpose.

Reference: https://leetcode.com/problems/rotate-image/

Complexity:

Time: O(n^2)

Space: O(1)

"""

from __future__ import annotations

def rotate(mat: list[list[int]]) -> list[list[int]]:

"""Rotate a square matrix 90 degrees clockwise in-place.

Args:

mat: Square matrix of size n x n.

Returns:

The same matrix, rotated 90 degrees clockwise.

Examples:

>>> rotate([[1, 2, 3], [4, 5, 6], [7, 8, 9]])

[[7, 4, 1], [8, 5, 2], [9, 6, 3]]

"""

if not mat:

return mat

mat.reverse()

for i in range(len(mat)):

for j in range(i):

mat[i][j], mat[j][i] = mat[j][i], mat[i][j]

return mat