src/advent04/advent04.hs

   1 import Data.List (sort)
   2 import Data.List.Split (splitOn)
   3 import qualified Data.Map.Strict as M
   4
   5 main :: IO ()
   6 main = do
   7         text <- readFile "data/advent04.txt"
   8         let passphrases = map parseLine $ lines text
   9         print $ part1 passphrases
  10         print $ part2 passphrases
  11
  12 part1 :: [[String]] -> Int
  13 part1 = length . filter (not . containsDuplicates)
  14
  15 part2 :: [[String]] -> Int
  16 part2 = length . filter (not . containsAnagrams)
  17
  18 parseLine :: String -> [String]
  19 parseLine = filter (not . null) . splitOn " "
  20
  21 frequency :: (Ord a) => [a] -> M.Map a Int
  22 frequency xs = M.fromListWith (+) [(x, 1) | x <- xs]
  23
  24 containsDuplicates :: [String] -> Bool
  25 containsDuplicates = (not . M.null) . M.filter (> 1) . frequency
  26
  27 containsAnagrams :: [String] -> Bool
  28 containsAnagrams = containsDuplicates . (map sort)