advent-of-code/2020/06-Custom_Customs/second.hs

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2023-03-13 21:36:59 +01:00
-- requires cabal install --lib split Unique
module Main (main) where
import Control.Monad (void, when)
import Data.List (intersect, foldl')
import Data.List.Split (splitOn)
import System.Exit (die)
exampleExpectedOutput = 6
parseInput :: String -> IO [String]
parseInput filename = do
input <- readFile filename
return $ map (foldl' intersect ['a'..'z'] . lines) $ splitOn "\n\n" input
compute :: [String] -> Int
compute = sum . map length
main :: IO ()
main = do
example <- parseInput "example"
let exampleOutput = compute example
when (exampleOutput /= exampleExpectedOutput) (die $ "example failed: got " ++ show exampleOutput ++ " instead of " ++ show exampleExpectedOutput)
input <- parseInput "input"
print $ compute input