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Arkham/Main.hs Secret

Created January 6, 2021 11:52
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{-# LANGUAGE DeriveGeneric #-}
module Main where
import qualified Data.Char as Char
import qualified Data.HashMap.Strict as HM
import Data.Hashable
import qualified Data.List.Split as S
import Data.Maybe (mapMaybe)
import GHC.Generics (Generic)
main :: IO ()
main = do
contents <- readFile "input.txt"
let entries = map parseEntry (S.splitOn "\n\n" contents)
print $ length $ filter isEntryValid entries
type PassportEntry = HM.HashMap PassportField String
data PassportField
= BirthYear
| IssueYear
| ExpirationYear
| Height
| HairColor
| EyeColor
| PassportId
| CountryId
deriving (Eq, Show, Generic)
instance Hashable PassportField
parseEntry :: String -> PassportEntry
parseEntry line =
HM.fromList $
mapMaybe parseTag $
S.splitWhen Char.isSpace line
parseTag :: String -> Maybe (PassportField, String)
parseTag value =
case S.splitOn ":" value of
["byr", byr] ->
Just (BirthYear, byr)
["iyr", iyr] ->
Just (IssueYear, iyr)
["eyr", eyr] ->
Just (ExpirationYear, eyr)
["hgt", height] ->
Just (Height, height)
["hcl", color] ->
Just (HairColor, color)
["ecl", color] ->
Just (EyeColor, color)
["pid", pid] ->
Just (PassportId, pid)
["cid", cid] ->
Just (CountryId, cid)
_ ->
requiredFields :: [PassportField]
requiredFields =
[ BirthYear,
isEntryValid :: PassportEntry -> Bool
isEntryValid entry =
all (`HM.member` entry) requiredFields
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