advent06.hs

   1 module Main(main) where
   2
   3 import Data.List (transpose)
   4 import Data.Char (isLetter)
   5 import qualified Data.Map.Lazy as Map
   6
   7
   8 input = "cxdnnyjw"
   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
  18 part1 :: [String] -> IO ()
  19 part1 message = do
  20     print $ map (fst) $ map (mostCommon) $ map (countedLetters) $ transpose message
  21
  22 part2 :: [String] -> IO ()
  23 part2 message = do
  24     print $ map (fst) $ map (leastCommon) $ map (countedLetters) $ transpose message
  25
  26
  27
  28 countedLetters :: String -> Map.Map Char Int
  29 countedLetters name = Map.fromListWith (+) [(c, 1) | c <- filter (isLetter) name]
  30
  31 mostCommon = Map.foldlWithKey (mostCommonP) ('a', 0)
  32
  33 mostCommonP (letter0, count0) letter count
  34     | count > count0 = (letter, count)
  35     | otherwise = (letter0, count0)
  36
  37 leastCommon = Map.foldlWithKey (leastCommonP) ('a', maxBound :: Int)
  38
  39 leastCommonP (letter0, count0) letter count
  40     | count < count0 = (letter, count)
  41     | otherwise = (letter0, count0)