advent06.hs

   1 -- Better version of advent06.hs, using more standard library functions.
   2
   3 module Main(main) where
   4
   5 import Data.List (transpose, maximum, minimum)
   6 import Data.Char (isLetter)
   7 import Data.Tuple (swap)
   8 import qualified Data.Map.Lazy as Map
   9
  10 main :: IO ()
  11 main = do
  12     text <- readFile "advent06.txt"
  13     let message = lines text
  14     part1 message
  15     part2 message
  16
  17 part1 :: [String] -> IO ()
  18 part1 message = do
  19     putStrLn $ map (fst) $ map (mostCommon) $ map (countedLetters) $ transpose message
  20
  21 part2 :: [String] -> IO ()
  22 part2 message = do
  23     putStrLn $ map (fst) $ map (leastCommon) $ map (countedLetters) $ transpose message
  24
  25 countedLetters :: String -> [(Char, Int)]
  26 countedLetters name = Map.toList $ Map.fromListWith (+) [(c, 1) | c <- filter (isLetter) name]
  27
  28 mostCommon :: [(Char, Int)] -> (Char, Int)
  29 mostCommon = swap . maximum . map (swap)
  30
  31 leastCommon :: [(Char, Int)] -> (Char, Int)
  32 leastCommon = swap . minimum . map (swap)