From eb8a9795edbd030bd872e3592a0d2eb434cc5ad9 Mon Sep 17 00:00:00 2001
From: Joscha <joscha@plugh.de>
Date: Sat, 5 Dec 2020 12:15:19 +0000
Subject: [PATCH] [hs] Clean up 2020_05 even more

---
 hs/src/Aoc/Y2020/D05.hs | 33 ++++++++++++---------------------
 1 file changed, 12 insertions(+), 21 deletions(-)

diff --git a/hs/src/Aoc/Y2020/D05.hs b/hs/src/Aoc/Y2020/D05.hs
index 8560e2d..e3924c2 100644
--- a/hs/src/Aoc/Y2020/D05.hs
+++ b/hs/src/Aoc/Y2020/D05.hs
@@ -3,50 +3,41 @@ module Aoc.Y2020.D05
   ) where
 
 import           Control.Monad
+
 import qualified Data.Set      as Set
 
 import           Aoc.Day
 import           Aoc.Parse
 
-data Pass = Pass
-  { fb :: [Bool]
-  , lr :: [Bool]
-  } deriving (Show, Eq, Ord)
+-- Ordered from least to most significant
+fromBin :: [Bool] -> Int
+fromBin bs = sum $ zipWith (*) (iterate (*2) 1) (map fromEnum bs)
 
-parser :: Parser [Pass]
+parser :: Parser [Int]
 parser = manyLines $ do
   fbs <- count 7 $ (False <$ char 'F') <|> (True <$ char 'B')
   lrs <- count 3 $ (False <$ char 'L') <|> (True <$ char 'R')
-  pure Pass { fb = fbs, lr = lrs }
+  pure $ fromBin $ reverse $ fbs ++ lrs
 
-calcNum :: [Bool] -> Int
-calcNum bs = sum $ zipWith (*) (iterate (*2) 1) (map fromEnum $ reverse bs)
-
-seatId :: Pass -> Int
-seatId p = 8 * calcNum (fb p) + calcNum (lr p)
-
-allSeats :: [Pass]
-allSeats = Pass
-  <$> sequenceA (replicate 7 [False, True])
-  <*> sequenceA (replicate 3 [False, True])
+allSeats :: [Int]
+allSeats = [0..1023]
 
 mySeats :: Set.Set Int -> [Int]
 mySeats taken = do
-  sid <- seatId <$> allSeats
+  sid <- allSeats
   guard $ (sid - 1) `Set.member` taken
   guard $ not $ sid `Set.member` taken
   guard $ (sid + 1) `Set.member` taken
   pure sid
 
-solver :: [Pass] -> IO ()
+solver :: [Int] -> IO ()
 solver ps = do
   putStrLn ">> Part 1"
-  print $ maximum $ map seatId ps
+  print $ maximum ps
 
   putStrLn ""
   putStrLn ">> Part 2"
-  let taken = Set.fromList $ map seatId ps
-  print $ mySeats taken
+  print $ mySeats $ Set.fromList ps
 
 day :: Day
 day = dayParse "2020_05" parser solver