Merge pull request #2866 from jeongoon/master

[ch-088/jeongoon] Perl, Raku, Haskell, Go, Common-lisp, Elm solution added.

1 files changed, 42 insertions, 0 deletions

diff --git a/challenge-086/jeongoon/haskell/ch-1.hs b/challenge-086/jeongoon/haskell/ch-1.hs
new file mode 100644
index 0000000000..59a46bb9ec
--- /dev/null
+++ b/challenge-086/jeongoon/haskell/ch-1.hs
@@ -0,0 +1,42 @@
+import System.Environment
+import System.Exit
+import Data.Char (isNumber)
+import Data.Maybe (isNothing, catMaybes)
+import Data.List (sort)
+
+{- tested with:
+runhaskell ch-1.hs  1 3 2 -1 -2 -3 6 7 9 1
+1 as 3 - 2 = 1
+-}
+
+usageMessage = "Usage: runhaskell ch-1.hs "
+               ++ "<target diff(positive integer)> <integer> ..."
+
+pairDifference _      [] = Nothing
+pairDifference target ls = pairdiff target (head sorted) (tail sorted) 1
+  where
+    sorted = sort ls
+    pairdiff _ _ [] _ = Nothing
+    pairdiff t f rst@(r:_) i = -- t: target, f: first, i: index
+      if i >= (length rst) then Nothing
+      else case ((rst !! i) - f) `compare` t of
+             LT -> pairdiff t f rst (succ i)
+             GT -> pairdiff t r rst 1
+             EQ -> Just (f, (rst !! i))
+
+main = do
+    (catMaybes.map (\nStr ->
+                      -- poor parser
+                       if (all (`elem` "0123456789+-") nStr)
+                       then Just(read nStr :: Int)
+                       else Nothing )) `fmap` getArgs
+      >>= ( \ints ->
+             let d = (head ints) in
+               if (length ints) < 2
+               then die usageMessage
+               else if d < 0
+               then die usageMessage
+               else case pairDifference d (tail ints) of
+                 Nothing    -> putStrLn "0"
+                 Just (a,b) -> putStrLn $ "1 as " ++ (show b) ++ " - "
+                               ++ (show a) ++ " = " ++ (show d) )