Done day 22

[advent-of-code-20.git] / advent22 / src / advent22.hs

diff --git a/advent22/src/advent22.hs b/advent22/src/advent22.hs
new file mode 100644 (file)
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+-- import Debug.Trace
+
+import Data.Text (Text)
+-- import qualified Data.Text as T
+import qualified Data.Text.IO as TIO
+
+import Data.Attoparsec.Text hiding (take)
+-- import Data.Attoparsec.Combinator
+import Control.Applicative
+-- import Control.Applicative.Combinators
+
+import qualified Data.Set as S
+import qualified Data.Sequence as Q
+import Data.Sequence (Seq (Empty, (:<|), (:|>)), (<|), (|>))
+
+type Deck = Q.Seq Int
+type Game = (Deck, Deck)
+
+data Player = P1 | P2 deriving (Show, Eq)
+
+
+main :: IO ()
+main = 
+  do  text <- TIO.readFile "data/advent22.txt"
+      let decks = successfulParse text
+      print decks
+      print $ play decks
+      print $ part1 decks
+      print $ part2 decks
+
+part1 decks = score $ winningDeck $ play decks
+part2 decks = score $ snd $ playRecursive decks S.empty
+
+play = until finished playRound 
+
+finished :: Game -> Bool
+finished (Empty, _)     = True
+finished (_,     Empty) = True
+finished (_,     _)     = False
+
+playRound :: Game -> Game
+playRound ((x :<| xs), (y :<| ys))
+  | x < y     = (xs,           ys |> y |> x)
+  | otherwise = (xs |> x |> y, ys)
+
+winningDeck game = case (winner game) of
+  P1 -> fst game
+  P2 -> snd game
+
+winner :: Game -> Player
+winner (Empty, ys) = P2
+winner (xs,    _)  = P1
+
+score :: Deck -> Int
+score = Q.foldrWithIndex (\i c s -> s + (i + 1) * c) 0 . Q.reverse
+
+
+playRecursive :: Game -> (S.Set Game) -> (Player, Deck)
+playRecursive (Empty, ys) _ = (P2, ys)
+playRecursive (xs, Empty) _ = (P1, xs)
+playRecursive g@(x :<| xs, y :<| ys) seen 
+  | g `S.member` seen = (P1, x :<| xs)
+  | (lengthAtLeast x xs) && (lengthAtLeast y ys) = playRecursive subG seen'
+  | otherwise = playRecursive compareG seen'
+  where seen' = S.insert g seen
+        (subWinner, _) = playRecursive (Q.take x xs, Q.take y ys) seen'
+        subG = updateDecks subWinner g
+        compareWinner = if x < y then P2 else P1
+        compareG = updateDecks compareWinner g
+
+
+updateDecks P1 (x :<| xs, y :<| ys) = (xs |> x |> y, ys)
+updateDecks P2 (x :<| xs, y :<| ys) = (xs, ys |> y |> x)
+
+lengthAtLeast n s = Q.length s >= n
+
+
+
+
+-- Parse the input file
+
+decksP = (,) <$> deckP <* (many endOfLine) <*> deckP
+
+headerP = string "Player " *> decimal *> ":" *> endOfLine
+
+deckP = Q.fromList <$> (headerP *> (decimal `sepBy` endOfLine))
+
+successfulParse :: Text -> Game
+successfulParse input = 
+  case parseOnly decksP input of
+    Left  _err -> (Q.empty, Q.empty) -- TIO.putStr $ T.pack $ parseErrorPretty err
+    Right decks -> decks