- Added Haskell solution by Ulrich Rieke.

1 files changed, 36 insertions, 0 deletions

diff --git a/challenge-124/ulrich-rieke/haskell/ch-2.hs b/challenge-124/ulrich-rieke/haskell/ch-2.hs
new file mode 100644
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+++ b/challenge-124/ulrich-rieke/haskell/ch-2.hs
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+module Challenge124_2
+  where
+import qualified Data.Set as Set
+import Data.List ( minimumBy , sort )
+
+combinations :: Int -> [a] -> [[a]]
+combinations 0 _ = [[]]
+combinations n xs = [ xs !! i : x | i <- [0..(length xs ) - 1 ] ,
+x <- combinations (n - 1 ) ( drop ( i + 1 ) xs ) ]
+
+findComplement :: [Int] -> [Int] -> [Int]
+findComplement numbers combi = Set.toList ( Set.fromList numbers Set.\\
+Set.fromList combi )
+
+solution :: [Int] -> String
+solution list = "Subset 1 = " ++ (show $ sort $ fst pair) ++ " " ++
+"Subset 2 = " ++ ( show $ sort $ snd pair )
+where
+  pair :: ([Int] , [Int] )
+  pair =  minimumBy myFunc listPairs
+  l :: Int
+  l = length list
+  allCombis :: [[Int]]
+  allCombis = if even l then combinations ( div l 2 ) list else
+  (combinations ( div l 2 ) list) ++ ( combinations ( div l 2 + 1 ) list)
+  listPairs :: [( [Int] , [Int] )]
+  listPairs = map (\combi -> ( combi , findComplement list combi ) )
+  allCombis
+  myFunc :: ([Int] , [Int] ) -> ([Int] , [Int] ) -> Ordering
+  myFunc pair1 pair2
+  | abs ( (sum $ fst pair1) - (sum $ snd pair1) ) <  abs ( (sum $ fst pair2
+    ) - (sum $ snd pair2) ) = LT
+  | abs ( (sum $ fst pair1) - (sum $ snd pair1) ) == abs ( (sum $ fst pair2
+    ) - (sum $ snd pair2) ) = EQ
+  | abs ( (sum $ fst pair1) - (sum $ snd pair1) ) > abs ( (sum $ fst pair2
+    ) - (sum $ snd pair2) ) = GT