.gitignore

@@ -23,3 +23,6 @@ cabal.project.local~
 .HTF/
 .ghc.environment.*
 
+
+# vscode
+.vscode

AdventOfCode2020.cabal

@@ -17,7 +17,7 @@ maintainer:          gael@depreeuw.dev
 extra-source-files:  CHANGELOG.md, README.md
 
 library
-  exposed-modules:     Day1, Day2, Day3
+  exposed-modules:     Day1, Day2, Day3, Day4
   -- other-modules:
   -- other-extensions:
   build-depends:       base ^>=4.13.0.0

Main.hs

@@ -3,9 +3,11 @@ module Main where
 import Day1 (day1)
 import Day2 (day2)
 import Day3 (day3)
+import Day4 (day4)
 
 main :: IO ()
 main = do
   day1
   day2
   day3
+  day4

src/Day4.hs

@@ -0,0 +1,158 @@
+{-# LANGUAGE OverloadedStrings #-}
+
+module Day4 (day4) where
+
+import Control.Applicative ((<|>))
+import Control.Monad (void)
+import qualified Data.Attoparsec.Text as P
+import qualified Data.Map as M
+import Data.Maybe (catMaybes)
+import qualified Data.Text as T
+
+data Height = CM Integer | IN Integer deriving (Show, Eq)
+
+data EyeColour = AMB | BLU | BRN | GRY | GRN | HZL | OTH deriving (Show, Eq)
+
+type BYR = Either String Integer
+
+type IYR = Either String Integer
+
+type EYR = Either String Integer
+
+type HGT = Either String Height
+
+type HCL = Either String String
+
+type ECL = Either String EyeColour
+
+type PID = Either String Integer
+
+type CID = T.Text
+
+data Passport = Passport
+  { byr :: BYR,
+    iyr :: IYR,
+    eyr :: EYR,
+    hgt :: HGT,
+    hcl :: HCL,
+    ecl :: ECL,
+    pid :: PID,
+    cid :: Maybe CID -- Definitely not a hack!
+  }
+  deriving (Eq, Show)
+
+parserPair :: P.Parser (T.Text, T.Text)
+parserPair = do
+  key <- P.count 3 P.letter
+  _ <- P.char ':'
+  value <- P.takeWhile1 (P.inClass "a-zA-Z0-9#")
+  return (T.pack key, value)
+
+parserEntry :: P.Parser (M.Map T.Text T.Text)
+parserEntry = M.fromList <$> parserPair `P.sepBy` (void P.space <|> P.endOfLine)
+
+parseBYR :: T.Text -> BYR
+parseBYR s = do
+  n <- P.eitherResult $ P.parse (P.count 4 P.digit) s
+  let n' = read n
+  if n' >= 1920 && n' <= 2002 then Right n' else Left (T.unpack s)
+
+parseIYR :: T.Text -> IYR
+parseIYR s = do
+  n <- P.eitherResult $ P.parse (P.count 4 P.digit) s
+  let n' = read n
+  if n' >= 2010 && n' <= 2020 then Right n' else Left (T.unpack s)
+
+parseEYR :: T.Text -> EYR
+parseEYR s = do
+  n <- P.eitherResult $ P.parse (P.count 4 P.digit) s
+  let n' = read n
+  if n' >= 2020 && n' <= 2030 then Right n' else Left (T.unpack s)
+
+parseCM :: P.Parser Height
+parseCM = do
+  n <- P.count 3 P.digit
+  _ <- P.string "cm"
+  let n' = read n
+  if n' >= 150 && n' <= 193
+    then return $ CM n'
+    else fail n
+
+parseIN :: P.Parser Height
+parseIN = do
+  n <- P.count 2 P.digit
+  _ <- P.string "in"
+  let n' = read n
+  if n' >= 59 && n' <= 76
+    then return $ IN n'
+    else fail n
+
+parseHGT :: T.Text -> HGT
+parseHGT s = P.eitherResult $ P.parse (parseCM <|> parseIN) s
+
+parseHCL :: T.Text -> HCL
+parseHCL s =
+  let p = P.char '#' *> P.count 6 (P.satisfy (P.inClass "a-f0-9"))
+   in P.eitherResult $ P.parse p s
+
+parseECL :: T.Text -> ECL
+parseECL s = do
+  let pAMB = AMB <$ P.string "amb"
+      pBLU = BLU <$ P.string "blu"
+      pBRN = BRN <$ P.string "brn"
+      pGRY = GRY <$ P.string "gry"
+      pGRN = GRN <$ P.string "grn"
+      pHZL = HZL <$ P.string "hzl"
+      pOTH = OTH <$ P.string "oth"
+      p = pAMB <|> pBLU <|> pBRN <|> pGRY <|> pGRN <|> pHZL <|> pOTH
+   in P.eitherResult $ P.parse p s
+
+parsePID :: T.Text -> PID
+parsePID s = fmap read (P.parseOnly (P.count 9 P.digit <* P.endOfInput) s)
+
+fromMap :: M.Map T.Text T.Text -> Maybe Passport
+fromMap m = do
+  byr <- m M.!? "byr"
+  let byr' = parseBYR byr
+  iyr <- m M.!? "iyr"
+  let iyr' = parseIYR iyr
+  eyr <- m M.!? "eyr"
+  let eyr' = parseEYR eyr
+  hgt <- m M.!? "hgt"
+  let hgt' = parseHGT hgt
+  hcl <- m M.!? "hcl"
+  let hcl' = parseHCL hcl
+  ecl <- m M.!? "ecl"
+  let ecl' = parseECL ecl
+  pid <- m M.!? "pid"
+  let pid' = parsePID pid
+  return $ Passport byr' iyr' eyr' hgt' hcl' ecl' pid' (m M.!? "cid")
+
+parserPassport :: P.Parser (Maybe Passport)
+parserPassport = fromMap <$> parserEntry
+
+parseList :: String -> [Maybe Passport]
+parseList s =
+  let p = parserPassport `P.sepBy` P.endOfLine
+   in case P.parseOnly p (T.pack s) of
+        Left s -> error (show s)
+        Right r -> r
+
+validatePassport :: Passport -> Bool
+validatePassport (Passport (Left _) _ _ _ _ _ _ _) = False
+validatePassport (Passport _ (Left _) _ _ _ _ _ _) = False
+validatePassport (Passport _ _ (Left _) _ _ _ _ _) = False
+validatePassport (Passport _ _ _ (Left _) _ _ _ _) = False
+validatePassport (Passport _ _ _ _ (Left _) _ _ _) = False
+validatePassport (Passport _ _ _ _ _ (Left _) _ _) = False
+validatePassport (Passport _ _ _ _ _ _ (Left _) _) = False
+validatePassport _ = True
+
+day4 :: IO ()
+day4 = do
+  r <- readFile "./input/day4"
+  putStr "[Day 4-1] # correct: "
+  let m = catMaybes . parseList $ r
+  print . length $ m
+  putStr "[Day 4-2] # more correct: "
+  print . length . filter validatePassport $ m