Day 04

2020/day04/day04.hs

@@ -0,0 +1,40 @@
+import Data.Char
+import Data.List
+import Data.List.Split
+
+main :: IO ()
+main = do
+  input <- map (unwords . lines) . splitOn "\n\n" <$> readFile "input"
+  print $ day4 input validateA
+  print $ day4 input validateB
+
+day4 :: [String] -> ([[String]] -> Bool) -> Int
+day4 input vldt = length $ filter vldt $ map (map (splitOn ":") . words) input
+
+validateA :: [[String]] -> Bool
+validateA =
+  null . (\\) ["byr", "iyr", "eyr", "hgt", "hcl", "ecl", "pid"] . map head
+
+validateB :: [[String]] -> Bool
+validateB input = validateA input && all val input
+  where
+    val (x:xs)
+      | "byr" <- x = pars >= 1920 && pars <= 2002
+      | "iyr" <- x = pars >= 2010 && pars <= 2020
+      | "eyr" <- x = pars >= 2020 && pars <= 2030
+      | "hgt" <- x =
+        case partition isDigit b of
+          (y, "cm") -> read y >= 150 && read y <= 193
+          (y, "in") -> read y >= 59 && read y <= 76
+          _ -> False
+      | "hcl" <- x =
+        (head b == '#') &&
+        all (`elem` (['0' .. '9'] `union` ['a' .. 'f'])) (tail b) &&
+        (length b == 7)
+      | "ecl" <- x = b `elem` ["amb", "blu", "brn", "gry", "grn", "hzl", "oth"]
+      | "pid" <- x = length b == 9 && null (dropWhile isDigit b)
+      | "cid" <- x = True
+      | _ <- x = False
+      where
+        pars = read b
+        b = head xs