September 2017 Update

Task/Find-the-missing-permutation/Haskell/find-the-missing-permutation-1.hs

@@ -0,0 +1,37 @@
+import Data.List ((\\), permutations, nub)
+import Control.Monad (join)
+
+missingPerm
+  :: Eq a
+  => [[a]] -> [[a]]
+missingPerm = (\\) =<< permutations . nub . join
+
+deficientPermsList :: [String]
+deficientPermsList =
+  [ "ABCD"
+  , "CABD"
+  , "ACDB"
+  , "DACB"
+  , "BCDA"
+  , "ACBD"
+  , "ADCB"
+  , "CDAB"
+  , "DABC"
+  , "BCAD"
+  , "CADB"
+  , "CDBA"
+  , "CBAD"
+  , "ABDC"
+  , "ADBC"
+  , "BDCA"
+  , "DCBA"
+  , "BACD"
+  , "BADC"
+  , "BDAC"
+  , "CBDA"
+  , "DBCA"
+  , "DCAB"
+  ]
+
+main :: IO ()
+main = print $ missingPerm deficientPermsList

Task/Find-the-missing-permutation/Haskell/find-the-missing-permutation-2.hs

@@ -0,0 +1,37 @@
+import Data.List (minimumBy, group, sort, transpose)
+import Data.Ord (comparing)
+
+missingPerm
+  :: Ord a
+  => [[a]] -> [a]
+missingPerm = ((head . minimumBy (comparing length) . group . sort) <$>) . transpose
+
+deficientPermsList :: [String]
+deficientPermsList =
+  [ "ABCD"
+  , "CABD"
+  , "ACDB"
+  , "DACB"
+  , "BCDA"
+  , "ACBD"
+  , "ADCB"
+  , "CDAB"
+  , "DABC"
+  , "BCAD"
+  , "CADB"
+  , "CDBA"
+  , "CBAD"
+  , "ABDC"
+  , "ADBC"
+  , "BDCA"
+  , "DCBA"
+  , "BACD"
+  , "BADC"
+  , "BDAC"
+  , "CBDA"
+  , "DBCA"
+  , "DCAB"
+  ]
+
+main :: IO ()
+main = print $ missingPerm deficientPermsList

Task/Find-the-missing-permutation/Haskell/find-the-missing-permutation.hs

@@ -1,16 +0,0 @@
-import Data.List
-import Control.Monad
-import Control.Arrow
-
-missingPerm :: Eq a => [[a]] -> [[a]]
-missingPerm = (\\) =<< permutations . nub . join
-
-deficientPermsList = ["ABCD","CABD","ACDB","DACB",
-                      "BCDA","ACBD","ADCB","CDAB",
-                      "DABC","BCAD","CADB","CDBA",
-                      "CBAD","ABDC","ADBC","BDCA",
-                      "DCBA","BACD","BADC","BDAC",
-                      "CBDA","DBCA","DCAB"]
-
-main = do
-    print $ missingPerm deficientPermsList