Initial data commit

Task/Sailors-coconuts-and-a-monkey-problem/Haskell/sailors-coconuts-and-a-monkey-problem.hs

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+import Control.Monad ((>=>))
+import Data.Maybe (mapMaybe)
+import System.Environment (getArgs)
+
+-- Takes the number of sailors and the final number of coconuts. Returns
+-- Just the associated initial number of coconuts and Nothing otherwise.
+tryFor :: Int -> Int -> Maybe Int
+tryFor s = foldr (>=>) pure $ replicate s step
+  where
+    step n
+      | n `mod` (s - 1) == 0 = Just $ n * s `div` (s - 1) + 1
+      | otherwise = Nothing
+
+-- Gets the number of sailors from the first command-line argument and
+-- assumes 5 as a default if none is given. Then uses tryFor to find the
+-- smallest solution.
+main :: IO ()
+main = do
+  args <- getArgs
+  let n =
+        case args of
+          [] -> 5
+          s:_ -> read s
+      a = head . mapMaybe (tryFor n) $ [n,2 * n ..]
+  print a