2D array traverse in a spiral pattern using recursion

Question

I am preparing for an interview and have been stuck on this issue for quite some time. Can someone please help me with the code. If not complete, then maybe its fragment? You are welcome..

Answer 1

Python 2, prints a two-dimensional nested list clockwise, from the top left corner to the center:

>>> def clockwise(r):
...     return list(r[0]) + clockwise(list(reversed(zip(*r[1:])))) if r else []
... 
>>> a = [ 
...   [ 1,  2,  3], 
...   [ 5,  6,  7], 
...   [ 9, 10, 11]]
>>> clockwise(a)
[1, 2, 3, 7, 11, 10, 9, 5, 6]
>>> a = [ 
...   [ 1,  2,  3,  4], 
...   [ 5,  6,  7,  8], 
...   [ 9, 10, 11, 12],
...   [13, 14, 15, 16]]
>>> clockwise(a)
[1, 2, 3, 4, 8, 12, 16, 15, 14, 13, 9, 5, 6, 7, 11, 10]

? clockwise r. , . , , , . ( ). . , , , . , ( ), .

, , Haskell:

import Data.List

clockwise :: [[a]] -> [a] 
clockwise (x:xs) = x ++ (clockwise $ reverse $ transpose $ xs) 
clockwise _      = []