IntMap -> Vector

haskell-version/haskell-version.cabal

@@ -16,8 +16,9 @@ extra-source-files:  README.md
 executable haskell-version
   hs-source-dirs:      src
   main-is:             Main.hs
+  ghc-options:         -O2
   default-language:    Haskell2010
   build-depends:       base >= 4.7 && < 5
                      , bytestring >= 0.10.8.1
                      , bytestring-lexing
-                     , containers >= 0.5.7.1
+                     , vector

haskell-version/src/Main.hs

@@ -1,23 +1,16 @@
 module Main where
 
 import qualified Data.ByteString.Char8 as C8
-import qualified Data.IntMap.Strict as M
-import Data.List
 import Data.ByteString.Lex.Integral
+import qualified Data.Vector.Unboxed as V
 
 toInt :: C8.ByteString -> Int
 toInt = readDecimal_
 
-processFile = do
-  bsLines <- C8.lines <$> C8.readFile "../ngrams.tsv"
-  let info = C8.splitWith (=='\t') <$> bsLines :: [[C8.ByteString]]
-  let m = foldl'
-             (\acc x -> let (_:key:val:_) = (x :: [C8.ByteString]) in M.insertWith (\new old -> old + new) (toInt key) (toInt val) acc)
-             M.empty
-             info
-  pure $ last $ sortOn snd (M.toList m)
+process bs = (i, xs V.! i) where
+  info = C8.splitWith (=='\t') <$> C8.lines bs
+  xs = V.unsafeAccumulate (+) (V.replicate 2009 0) . V.fromList 
+     $ map (\(_:key:val:_) -> (toInt key, toInt val)) info
+  i = V.maxIndex xs
 
-main :: IO ()
-main = do
-  x <- processFile
-  print x
+main = print . process =<< C8.readFile "../ngrams.tsv"