Create a function that flips a horizontal array into a vertical array, and a vertical array into a horizontal array.

In other words, take an 1 x n array (1 row + n columns) and flip it into a n x 1 array (n rows and 1 column), and vice versa.

Examples

flip_array([1, 2, 3, 4]) ➞ [[1], [2], [3], [4]]
# Take a horizontal array and flip it vertical.

flip_array([[5], [6], [9]]) ➞ [5, 6, 9]
# Take a vertical array and flip it horizontal.

flip_array([]) ➞ []

Notes

If given an empty array [], return an empty array [].