Spiralled Arrays

turn [1,2,3,4,5,6,7,8,9] into [9,2,3,8,1,4,7,6,5]. Make it work for an arbitrary array of size n^2. equally acceptable is [[1,2,3],[4,5,6],[7,8,9]] into [[9,2,3],[8,1,4],[7,6,5]].

how's it done?

pseudocode'll do

>>1
Say what? What kind of transformation do you want? [9,2,3,8,1,4,7,6,5] doesn't look like a spiral to me.

print [9,2,3,8,1,4,7,6,5] in rows of 3

9 2 3
8 1 4
7 6 5

i should add that the elements of the array aren't necessarily ordered. it has to be able to go from ["the","spiral","was","made","from","an","array","yes","indeed"] to ["indeed","spiral","was","yes","the","made","array","an","from"]

from homework import spiral_array

>>5 win

>>1
I managed to creat a haskell solution in 4 lines of code using foldr

Post your solution, and I will post mine

i don't have a solution. and contrary to the cynicism of >>5, this isn't homework, because a) it's summer, b) i've finished school, c) i've not taken a computer science subject at all

great, so none of you can just give me pseudocode on how to approach this? with an explanation? good work internet!

trolled

>>10

wtf?

>>9
Bitch, bitch, bitch. Complain, complain, complain.

>>9
I'm not here to help you or anyone else, bitch. If sometimes I do so it's just because I found the problem in question interesting.

What if n is an even number?

this VERY UGLY code may be a hint on how to do it. you'll have to rewrite it though, it's written in haskell in a sucky imperative style, which does not really suit haskell. anyway, I'm not even sure it works. basically, the idea is, you start with an empty matrix (list of lists). you keep a sort of a pointer, which stats the position and the direction you're going in the spiral. the function travels gives you the next pointer.
so, basically, you start with the first pointer, insert the item, then get the next pointer, insert the item, etc. if you want to do it in a true functional style (which would be cleaner than this piece of shit I threw together right now), collect the pointers, then sort them by the position, and pick up (i.e. map a selecting function) the items).

travel _ ("up",0,j) = ("right", 0, j + 1)
travel _ ("up",i,j) = ("up", i - 1, j)
travel n ("right", i, j) | n == j    = ("down", i - 1, j)
                         | otherwise = ("right", i, j + 1)
-- fill up the rest yourself

group [] _ = []
group l n = take 3 l : group (drop n l)

makeList _ 0 = []
makeList i n = i:makeList i (n - 1)

start i n = makeList (makeList i n) n

inserte e 0 x:xs = e:xs
inserte e p x:xs = x:inserte e (p - 1) xs

insert 0 j e x:xs = inserte e j x : xs
insert i j e x:xs = x : insert (i - 1) j e xs

spiral x:xs = concat (loop n (start x n) x:xs ("up", n div 2 + 1, n div 2 + 1))
                where n = sqrt (length x:xs)

loop _ matrix [] _ = matrix
loop n matrix x:xs (direction, i, j) = loop n (insert i j x matrix) xs (travel n (direction, i, j))

Pseudocode:

1. Create array.
2. ?????
3. [1,2,3,4,5,6,7,8,9] turns into [9,2,3,8,1,4,7,6,5]
4. return mudkips

>>1
1. flattern your first array (ie [[1,2,3],[4,5,6],[7,8,9]] turns into [1,2,3,4,5,6,7,8,9])
2. shuffle elements manually

have you tried asking it politely

import List (transpose)

rotate = reverse . transpose

spiral (x:xs) = concat $ spiral' xs [[x]]
    where spiral' [] s = s
          spiral' ys s = let n = length $ head s
                         in spiral' (drop n ys) (rotate $ take n ys : s)

lisp hackers would use arc,

(= rotate (. reverse transpose))
(spiral (: x xs) (($ concat spiral') xs) ((x)))
    (= (where spiral' () s) s)
          ((spiral' ys s = (let (n ($ length head) s)))
                         (in spiral' (drop n ys) (($ rotate take) n (: ys s))))

 -- Paul graham

>>14

then n is divisible by 2

>>18

what part of the first few posts weren't polite, up until >>5 decided to be a cock?

>>21
>>9

>>22
>>5 >>6 >>7

Right, but >>9 appeared to be the op. That's also who the post was likely directed at. Anyway, what's your fixation on >>5 and the posts before >>5 ?

Thread over.

>>19
now that's a cool solution ;_;
(i'm >>15 btw)

LISP

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