advent06.hs

   1 module Main(main) where
   2
   3 import Data.List (last, intersperse, sortBy, intercalate, isInfixOf, transpose)
   4 import Data.List.Split (splitOn)
   5 import Data.Char (isLetter, ord, chr)
   6 import qualified Data.Map.Lazy as Map
   7
   8
   9 input = "cxdnnyjw"
  10
  11 main :: IO ()
  12 main = do
  13     text <- readFile "advent06.txt"
  14     let message = lines text
  15     part1 message
  16     part2 message
  17
  18
  19 part1 :: [String] -> IO ()
  20 part1 message = do
  21     print $ map (fst) $ map (mostCommon) $ map (countedLetters) $ transpose message
  22
  23 part2 :: [String] -> IO ()
  24 part2 message = do
  25     print $ map (fst) $ map (leastCommon) $ map (countedLetters) $ transpose message
  26
  27
  28
  29 countedLetters :: String -> Map.Map Char Int
  30 countedLetters name = Map.fromListWith (+) [(c, 1) | c <- filter (isLetter) name]
  31
  32 mostCommon = Map.foldlWithKey (mostCommonP) ('a', 0)
  33
  34 mostCommonP (letter0, count0) letter count
  35     | count > count0 = (letter, count)
  36     | otherwise = (letter0, count0)
  37
  38 leastCommon = Map.foldlWithKey (leastCommonP) ('a', maxBound :: Int)
  39
  40 leastCommonP (letter0, count0) letter count
  41     | count < count0 = (letter, count)
  42     | otherwise = (letter0, count0)