Merge branch 'master' of https://github.com/manwar/perlweeklychallenge-club

1 files changed, 53 insertions, 0 deletions

diff --git a/challenge-083/jeongoon/haskell/ch-2.hs b/challenge-083/jeongoon/haskell/ch-2.hs
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+import System.Environment
+import System.Exit
+import Data.Char (isNumber)
+import Data.Maybe (isJust, catMaybes)
+import Data.List (sum)
+import Combinations (combinations)
+
+
+{- test with:
+   runhaskell ch-2.hs 12 7 4 # answer: 12
+   runhaskell ch-2.hs 12 7 4 5 6 9 20 12 7 4 5 6 9 20 9 4 2 1 13 8 # answer: 6
+ # or in order to get faster result, you can compile and execute:
+   ghc ch-2.hs
+   ./ch-2 12 7 4 5 6 9 20 12 7 4 5 6 9 20 9 4 2 1 13 8 # answer: 6
+-}
+
+answerFlipArray :: (Integral a) => [a] -> Int
+answerFlipArray nums
+  | totalSum == 1 = 0
+  | otherwise = answerWith totalSum totalLen numCombis
+  where
+    totalSum  = sum nums
+    totalLen  = length nums
+    halfLen   = totalLen `div` 2
+    numCombis = (foldr1 (++) .
+                    map (combinations nums))
+                   [ 1 .. halfLen ]
+
+    answerWith _      minElems [] = minElems
+    answerWith minSum minElems (aCombi:otherCombis) =
+      case (positiveSum `compare` minSum) of
+        LT -> answerWith positiveSum newElems otherCombis
+        EQ -> answerWith minSum (min newElems minElems) otherCombis
+        GT -> answerWith minSum minElems otherCombis
+      where
+        len  = length aCombi
+        sm   = sum aCombi
+        sm'  = totalSum - sm
+        (positiveSum, newElems) =
+            case (sm `compare` sm') of
+              LT -> ( sm' - sm, len )
+              EQ -> (        0, (min len (totalLen - len)) )
+              GT -> ( sm - sm', (totalLen - len) )
+
+main = do
+    (catMaybes.map (\nStr ->
+                       if (all isNumber nStr) then Just(read nStr :: Int)
+                       else Nothing )) `fmap` getArgs
+      >>= (\nums ->
+              if length nums < 1 then
+                die "Usage: runhaskell ch-2.hs <natural num> ..."
+              else
+                putStrLn $ show ( answerFlipArray nums ) )