new files

Task/Best-shuffle/Haskell/best-shuffle-1.hs

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+import Data.Function (on)
+import Data.List
+import Data.Maybe
+import Data.Array
+import Text.Printf
+
+main = mapM_ f examples
+  where examples = ["abracadabra", "seesaw", "elk", "grrrrrr", "up", "a"]
+        f s = printf "%s, %s, (%d)\n" s s' $ score s s'
+          where s' = bestShuffle s
+
+score :: Eq a => [a] -> [a] -> Int
+score old new = length $ filter id $ zipWith (==) old new
+
+bestShuffle :: (Ord a, Eq a) => [a] -> [a]
+bestShuffle s = elems $ array bs $ f positions letters
+  where positions =
+            concat $ sortBy (compare `on` length) $
+            map (map fst) $ groupBy ((==) `on` snd) $
+            sortBy (compare `on` snd) $ zip [0..] s
+        letters = map (orig !) positions
+
+        f [] [] = []
+        f (p : ps) ls = (p, ls !! i) : f ps (removeAt i ls)
+          where i = fromMaybe 0 $ findIndex (/= o) ls
+                o = orig ! p
+
+        orig = listArray bs s
+        bs = (0, length s - 1)
+
+removeAt :: Int -> [a] -> [a]
+removeAt 0 (x : xs) = xs
+removeAt i (x : xs) = x : removeAt (i - 1) xs

Task/Best-shuffle/Haskell/best-shuffle-2.hs

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+bestShuffle :: Eq a => [a] -> [a]
+bestShuffle s = minimumBy (compare `on` score s) $ permutations s