AOC 2022 Day 2

daytwo.hs

module DayTwo (partOne, partTwo) where

import qualified Data.Text as T
import qualified Data.Text.IO as TI
import qualified Data.Maybe as M
import qualified Data.List as L

data Outcome = Win | Loss | Tie deriving (Eq, Show)
data Move = Rock | Paper | Scissor deriving (Eq, Show)
data Game = PartOneGame { us :: Move, them :: Move } |
            PartTwoGame { requiredOutcome :: Outcome, them :: Move } deriving (Eq, Show)

playMatch :: Move -> Move -> Outcome
playMatch Rock Scissor = Win
playMatch Paper Rock = Win
playMatch Scissor Paper = Win
playMatch ourMatchMove theirMatchMove = if ourMatchMove == theirMatchMove then Tie else Loss

scoreRound :: Num a => Game -> a
scoreRound PartOneGame{us=ourMove, them=theirMove} = (scoreShape ourMove) + (scoreOutcome $ playMatch ourMove theirMove)
  where
    scoreOutcome Win = 6
    scoreOutcome Tie = 3
    scoreOutcome Loss = 0
    scoreShape Rock = 1
    scoreShape Paper = 2
    scoreShape Scissor = 3

scoreRound PartTwoGame{requiredOutcome=outcome, them=theirMove} = scoreRound $ PartOneGame { us=requiredMove, them=theirMove}
  where
    requiredToWinAgainst x = M.fromJust $ L.find (\candidate -> (playMatch candidate x) == Win) allMoves
    requiredToLoseAgainst x = M.fromJust $ L.find (\candidate -> (playMatch candidate x) == Loss) allMoves
    getRequiredMove Win = requiredToWinAgainst theirMove
    getRequiredMove Loss = requiredToLoseAgainst theirMove
    getRequiredMove Tie = theirMove
    requiredMove = getRequiredMove outcome
    allMoves = [Rock, Paper, Scissor]


parse :: T.Text -> Maybe Game
parse row = do
  theirMove <- charToMove $ (T.unpack row) !! 0
  ourMove <- charToMove $ (T.unpack row) !! 2
  return $ PartOneGame ourMove theirMove
  where
    charToMove 'A' = Just Rock
    charToMove 'B' = Just Paper
    charToMove 'C' = Just Scissor
    charToMove 'X' = Just Rock
    charToMove 'Y' = Just Paper
    charToMove 'Z' = Just Scissor
    charToMove _ = Nothing


parsePartTwo :: T.Text -> Maybe Game
parsePartTwo row = do
  theirMove <- charToMove $ (T.unpack row) !! 0
  outcome <- charToOutcome $ (T.unpack row) !! 2
  return $ PartTwoGame { requiredOutcome = outcome, them = theirMove }
  where
    charToMove 'A' = Just Rock
    charToMove 'B' = Just Paper
    charToMove 'C' = Just Scissor
    charToMove _ = Nothing
    charToOutcome 'X' = Just Loss
    charToOutcome 'Y' = Just Tie
    charToOutcome 'Z' = Just Win
    charToOutcome _ = Nothing


partOne :: IO Integer
partOne = do
  input <- TI.readFile "/users/wailee.feman/Downloads/input.txt"
  let inputLines = T.lines input
      games = M.catMaybes $ map parse inputLines
      answer = sum $ map scoreRound games
  return answer


partTwo :: IO Integer
partTwo = do
  input <- TI.readFile "/path/to/input.txt"
  let inputLines = T.lines input
      games = M.catMaybes $ map parsePartTwo inputLines
      answer = sum $ map scoreRound games
  return answer