module Exercise_7 where
  import Data.Function
  import Data.List
  import Data.Text (splitOn, pack, unpack)
  import Data.Maybe

  {-WETT-}
  comp :: Eq b => [(Integer,(a,b))] -> [(Integer,(b,c))] -> [(Integer,(a,c))]
  comp [] _ = []
  comp ((distx, (a,b)):xs) ys = map (\(disty, (_,d))-> (distx+disty, (a,d))) ys' ++ comp xs ys
    where ys' = filter ((==b).fst.snd) ys

  partitionSet :: Eq a => [(Integer,(a,a))]-> [[(Integer,(a,a))]]
  partitionSet [] = []
  partitionSet set = part1 : partitionSet part2 where (part1, part2) =  partition (on (==) snd $ head set) set

  trancl :: Eq a => [(Integer,(a,a))] -> [(Integer,(a,a))]
  trancl set = 
    if length cache == length set then cache else trancl cache where 
      cache = map (minimumBy (on compare fst)) . partitionSet $ comp set set ++ set
  {-TTEW-}