def rotate(m):
    n = len(m)
    c = int((n + 1) / 2)
    f = int(n / 2)
    for x in range(c):
        for y in range(f):
            m[x][y], m[n - 1 - y][x] = m[n - 1 - y][x], m[x][y]
            m[n - 1 - y][x], m[n - 1 - x][n - 1 - y] = m[n - 1 - x][n - 1 - y], m[n - 1 - y][x]
            m[n - 1 - x][n - 1 - y], m[y][n - 1 - x] = m[y][n - 1 - x], m[n - 1 - x][n - 1 - y]
    return m


if __name__ == "__main__":
    a = [[1, 2], [3, 4]]
    a = rotate(a)
    assert (a[0][0] == 3)
    assert (a[0][1] == 1)
    assert (a[1][0] == 4)
    assert (a[1][1] == 2)
    a = [[1, 2, 3], [4, 5, 6], [6, 7, 8]]
    a = rotate(a)
    assert (a[0][0] == 6)
    assert (a[0][1] == 4)
    assert (a[0][2] == 1)
    assert (a[1][0] == 7)
    assert (a[1][1] == 5)
    assert (a[1][2] == 2)
    assert (a[2][0] == 8)
    assert (a[2][1] == 6)
    assert (a[2][2] == 3)