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December 15, 2023 13:48
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Day Twelve
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| {-# LANGUAGE OverloadedStrings #-} | |
| module DayTwelve where | |
| import qualified Data.Text as T | |
| import Data.Ratio ((%)) | |
| import qualified Data.List as L | |
| import qualified Text.Read as TR | |
| import Debug.Trace (traceShowId, traceShow) | |
| import qualified Data.Maybe as M | |
| import qualified Data.Map as DM | |
| import qualified Data.Set as S | |
| import qualified Data.List.Split as DLS | |
| import qualified Data.Range as R | |
| import Data.Range ((+=+), (+=*)) | |
| import Safe (atDef, atMay, minimumMay, headMay, headDef) | |
| -- SETUP | |
| data Tile = Working | Broken | Unknown deriving (Eq, Ord) | |
| data Row = Row [Tile] [Int] deriving (Eq, Show, Ord) | |
| getTiles (Row tiles _) = tiles | |
| getSegmentSpecification (Row _ segments) = segments | |
| rowSize = length . getTiles | |
| instance Show Tile where | |
| show Unknown = "?" | |
| show Broken = "#" | |
| show _ = "." | |
| edgecaseRow = parseRow ".?##???.#?.... 3,2" | |
| testRows :: [T.Text] | |
| testRows = ["???.### 1,1,3", | |
| ".??..??...?##. 1,1,3", | |
| "?#?#?#?#?#?#?#? 1,3,1,6", | |
| "????.#...#... 4,1,1", | |
| "????.######..#####. 1,6,5", | |
| "?###???????? 3,2,1"] | |
| parseTile '#' = Broken | |
| parseTile '?' = Unknown | |
| parseTile _ = Working | |
| tails items@(h:r) = items:(tails r) | |
| tails [] = [] | |
| cacheable bigRow@(Row tiles sizes) = do | |
| subInstructions <- tails (sizes) | |
| subTiles <- tails $ drop 10 tiles | |
| [Row subTiles subInstructions] | |
| expandRow times row = Row expanded instructions | |
| where expanded = L.intercalate [Unknown] $ take times $ cycle $ [getTiles row] | |
| instructions = concat $ take times $ cycle [getSegmentSpecification row] | |
| parseRow :: T.Text -> Row | |
| parseRow row = Row tilesList sizesList | |
| where sizesList :: [Int] | |
| sizesList = M.catMaybes $ map (TR.readMaybe . T.unpack) $ T.split (== ',') sizes | |
| layout:sizes:_ = T.split (== ' ') row | |
| tilesList = map parseTile (T.unpack layout) | |
| fastSolutionCount remainingRow@(Row tiles []) cache = if (any (== Broken) tiles) then 0 else 1 | |
| fastSolutionCount remainingRow@(Row tiles toPlace@(currentTask:rest)) cache | |
| | DM.member remainingRow cache = cache DM.! remainingRow | |
| | chopOutBoring remainingRow /= remainingRow = fastSolutionCount (chopOutBoring remainingRow) cache | |
| | otherwise = sum childAnswers | |
| where lp = legalPlacements remainingRow currentTask | |
| childAnswers = map recur lp | |
| recur newPlacementIndex = fastSolutionCount (Row (drop n tiles) rest) cache | |
| where n = newPlacementIndex + currentTask + 1 | |
| -- this just skips the fast-lookup step on the first level of recursion | |
| getCountForCache remainingRow@(Row tiles []) cache = if (any (== Broken) tiles) then 0 else 1 | |
| getCountForCache remainingRow@(Row tiles toPlace@(currentTask:rest)) cache | |
| | chopOutBoring remainingRow /= remainingRow = fastSolutionCount (chopOutBoring remainingRow) cache | |
| | otherwise = sum childAnswers | |
| where lp = legalPlacements remainingRow currentTask | |
| childAnswers = map recur lp | |
| recur newPlacementIndex = fastSolutionCount (Row (drop n tiles) rest) cache | |
| where n = newPlacementIndex + currentTask + 1 | |
| legalPlacements :: Row -> Int -> [Int] | |
| legalPlacements row@(Row tiles _) placingSize = filter canPlace indices | |
| where canPlace idx = inMultirange usable ourRange && (avoidsMessyOverlaps broken ourRange) | |
| where ourRange = (idx +=+ (idx + placingSize - 1)) | |
| usable = usableIndices row | |
| broken = brokenIndices row | |
| indices = 0 `enumFromTo` max | |
| nextBrokenSpot = fmap inc $ headMay $ L.elemIndices Broken tiles | |
| inc x = x + 1 | |
| max = head $ M.catMaybes [nextBrokenSpot, Just ((rowSize row) - placingSize)] | |
| avoidsMessyOverlaps world current = (all (inMultirange [current]) potentialHits) && (head (R.joinRanges [current])) `elem` (R.joinRanges (current:world)) | |
| where potentialHits = filter (R.rangesAdjoin current) world | |
| chopOutBoring row@(Row tiles sizes) = Row newTiles sizes | |
| where newTiles = dropWhile (== Working) tiles | |
| usableIndices row = R.joinRanges $ map R.SingletonRange $ (L.elemIndices Broken tiles) ++ (L.elemIndices Unknown tiles) | |
| where tiles = getTiles row | |
| unknownIndices row = R.joinRanges $ map R.SingletonRange $ (L.elemIndices Unknown tiles) | |
| where tiles = getTiles row | |
| brokenIndices row = R.joinRanges $ map R.SingletonRange (L.elemIndices Broken tiles) | |
| where tiles = getTiles row | |
| inMultirange ranges candidate = R.intersection ranges cr == cr | |
| where cr = R.joinRanges [candidate] | |
| partTwo copiesCount row = fastSolutionCount bigRow builtCache | |
| where bigRow = expandRow copiesCount row | |
| cacheKeys = cacheable bigRow | |
| builtCache = DM.fromList $ map (\x -> (x, getCountForCache x builtCache)) cacheKeys | |
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