Rotate Image

A square image is stored as an n x n grid of pixel values. Write rotate_clockwise(grid) that turns the image 90 degrees clockwise, changing grid in place. It returns None; the caller looks at the mutated grid.

After the turn, the old top row becomes the new right column, the old left column becomes the new top row, and so on.

g = [[1, 2, 3],
     [4, 5, 6],
     [7, 8, 9]]
rotate_clockwise(g)
g   # [[7, 4, 1],
    #  [8, 5, 2],
    #  [9, 6, 3]]

g = [[1, 2],
     [3, 4]]
rotate_clockwise(g)
g   # [[3, 1],
    #  [4, 2]]

• 1 <= n <= 500; values are in [-1000, 1000].
• Don't build a second n x n grid and copy it back: move the values around inside grid itself.
• Aim for O(n²) time and O(1) extra space.