1 files changed, 54 insertions, 0 deletions
diff --git a/2020/22a.hs b/2020/22a.hs
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+module Day22A where
+
+import System.Environment (getArgs)
+import Text.Printf
+import Data.List.Split (splitOn)
+
+-- Types
+-- Top = First
+type Deck = [Int];
+
+-- (P1, P2)
+type State = (Deck, Deck);
+
+-- Parsing
+
+parseDeck :: String -> Deck
+parseDeck = map read . tail . lines
+
+-- Parse the input
+parseInput :: String -> State
+parseInput xs = (p1, p2)
+      where [p1, p2] = map parseDeck $ splitOn "\n\n" xs
+
+-- Parse a file given the path
+-- Returns list of instructions
+parseFromFile :: String -> IO State
+parseFromFile s = do 
+                   contents <- readFile s;
+                   return $ parseInput contents;
+
+takeTurn :: State -> State
+takeTurn (c1:p1, c2:p2) | c1 > c2 = (p1 ++ [c1, c2], p2)
+                        | otherwise = (p1, p2 ++ [c2, c1])
+takeTurn ([], _) = error "game is over!"
+takeTurn (_, []) = error "game is over!"
+
+getWinner :: State -> Deck
+getWinner (p1, []) = p1
+getWinner ([], p2) = p2
+getWinner s = getWinner $ takeTurn s
+
+getScore :: Deck -> Int
+getScore d = sum $ zipWith (*) (reverse [1..length d]) d
+
+-- runghc --ghc-arg='-package split' 22a.hs inputs/day22
+main :: IO ()
+main = do 
+        args <- getArgs;
+        s <- parseFromFile (head args);
+
+        let winnerScore = getScore $ getWinner s;
+        printf "Answer = %d\n" winnerScore :: IO ();
+
+        return ();