From 5a89816e03831e8b905d8f8fa2bd44c6decdfb7a Mon Sep 17 00:00:00 2001
From: Joscha <joscha@plugh.de>
Date: Wed, 16 Dec 2020 16:51:32 +0000
Subject: [PATCH] [hs] Solve 2020_16 part 1

---
 hs/src/Aoc/Y2020.hs     |  2 ++
 hs/src/Aoc/Y2020/D16.hs | 52 +++++++++++++++++++++++++++++++++++++++++
 2 files changed, 54 insertions(+)
 create mode 100644 hs/src/Aoc/Y2020/D16.hs

diff --git a/hs/src/Aoc/Y2020.hs b/hs/src/Aoc/Y2020.hs
index 975d004..2e29ab8 100644
--- a/hs/src/Aoc/Y2020.hs
+++ b/hs/src/Aoc/Y2020.hs
@@ -18,6 +18,7 @@ import qualified Aoc.Y2020.D12 as D12
 import qualified Aoc.Y2020.D13 as D13
 import qualified Aoc.Y2020.D14 as D14
 import qualified Aoc.Y2020.D15 as D15
+import qualified Aoc.Y2020.D16 as D16
 
 year :: Year
 year = Year 2020
@@ -36,4 +37,5 @@ year = Year 2020
   , (13, D13.day)
   , (14, D14.day)
   , (15, D15.day)
+  , (16, D16.day)
   ]
diff --git a/hs/src/Aoc/Y2020/D16.hs b/hs/src/Aoc/Y2020/D16.hs
new file mode 100644
index 0000000..30132b4
--- /dev/null
+++ b/hs/src/Aoc/Y2020/D16.hs
@@ -0,0 +1,52 @@
+{-# LANGUAGE OverloadedStrings #-}
+
+module Aoc.Y2020.D16
+  ( day
+  ) where
+
+import           Control.Monad
+
+import qualified Data.Map      as Map
+import qualified Data.Text     as T
+
+import           Aoc.Day
+import           Aoc.Parse
+
+data Input = Input
+  { iFields        :: Map.Map T.Text [(Int, Int)]
+  , iMyTicket      :: [Int]
+  , iNearbyTickets :: [[Int]]
+  } deriving (Show)
+
+parser :: Parser Input
+parser = do
+  fields <- Map.fromList <$> many (fieldLine <* newline)
+  void $ string "\nyour ticket:\n"
+  myTicket <- ticket <* newline
+  void $ string "\nnearby tickets:\n"
+  nearbyTickets <- many (ticket <* newline)
+  pure $ Input fields myTicket nearbyTickets
+  where
+    fieldLine = do
+      name <- takeWhileP Nothing $ \c -> (c /= ':') && (c /= '\n')
+      void $ string ": "
+      ranges <- sepBy ((,) <$> (decimal <* string "-") <*> decimal) (string " or ")
+      pure (name, ranges)
+    ticket = decimal `sepBy` string ","
+
+valid :: Int -> [(Int, Int)] -> Bool
+valid n = any (\(a, b) -> a <= n && n <= b)
+
+findValid :: Map.Map T.Text [(Int, Int)] -> Int -> [T.Text]
+findValid fields n = map fst $ filter (valid n . snd) $ Map.toList fields
+
+anyValid :: Map.Map T.Text [(Int, Int)] -> Int -> Bool
+anyValid fields = not . null . findValid fields
+
+solver :: Input -> IO ()
+solver i = do
+  putStrLn ">> Part 1"
+  print $ sum $ filter (not . anyValid (iFields i)) $ concat $ iNearbyTickets i
+
+day :: Day
+day = dayParse parser solver