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optimize day5 to use a HashSet

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JasterV 2025-03-25 23:56:12 +01:00
parent e8fadacad1
commit ed7e95b59d
1 changed files with 8 additions and 7 deletions
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15
src/Day5.hs
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@ -1,8 +1,9 @@
module Day5 (ParseError, partOne, partTwo) where
import qualified Data.Bifunctor as BF
import Data.HashSet (HashSet)
import qualified Data.HashSet as HashSet
import Data.List (sortBy)
import Data.Set (Set, fromList, member)
import qualified Data.Text as T
import Data.Text.Read (decimal)
@ -23,18 +24,18 @@ partTwo input = do
(rules, updates) <- parseInput input
return $ sum $ map (middleElem . sortUpdate rules) $ filter (not . isValidUpdate rules) updates
isValidUpdate :: Set Rule -> Update -> Bool
isValidUpdate :: HashSet Rule -> Update -> Bool
isValidUpdate rules update = sortUpdate rules update == update
sortUpdate :: Set Rule -> Update -> Update
sortUpdate :: HashSet Rule -> Update -> Update
sortUpdate rules = sortBy compareByRules
where
compareByRules x y = if member (x, y) rules then LT else GT
compareByRules x y = if HashSet.member (x, y) rules then LT else GT
middleElem :: Update -> Int
middleElem update = update !! (length update `div` 2)
parseInput :: String -> Either ParseError (Set Rule, [Update])
parseInput :: String -> Either ParseError (HashSet Rule, [Update])
parseInput content = case T.splitOn separator text of
[left, right] -> do
rules <- parseRules left
@ -45,8 +46,8 @@ parseInput content = case T.splitOn separator text of
text = T.pack content
separator = T.pack "\n\n"
parseRules :: T.Text -> Either ParseError (Set Rule)
parseRules rules = fromList <$> mapM parseRule (T.lines rules)
parseRules :: T.Text -> Either ParseError (HashSet Rule)
parseRules rules = HashSet.fromList <$> mapM parseRule (T.lines rules)
where
parseRule rule = case T.split (== '|') rule of
[left, right] -> do