kosugi

-- -*- coding: utf-8 -*-
import Test.HUnit

deal :: Int -> String -> [String]
deal n s = deal_ 0 (take n $ repeat "") (take ((length s) - (length s `mod` n)) s)
  where deal_ _ ys [] = ys
        deal_ m ys (x:xs) = deal_ ((m + 1) `mod` n) ((take m ys) ++ [(ys!!m) ++ [x]] ++ (drop (m + 1) ys)) xs

tests = test [
  ["111", "222", "333"] ~=? deal 3 "123123123",