45 lines
1.6 KiB
Haskell
45 lines
1.6 KiB
Haskell
import Aoc
|
|
import Data.List.Split ( splitOn )
|
|
import Control.Arrow ( second, first )
|
|
import Data.List ( nub, partition, sort )
|
|
import Data.Maybe ( fromMaybe )
|
|
|
|
parseFile :: [String] -> ([(Int, [Int])], [[Int]])
|
|
parseFile lines =
|
|
let
|
|
[rules, pages] = splitOn [""] lines
|
|
rules' = map (pair . map read . splitOn "|") rules
|
|
mentioned = nub $ concatMap unpair rules'
|
|
getAll a = map snd $ filter ((==a) . fst) rules'
|
|
in
|
|
(zip mentioned (map getAll mentioned), map (map read . splitOn ",") pages)
|
|
|
|
takeMiddle :: [a] -> a
|
|
takeMiddle xs = xs !! (length xs `div` 2)
|
|
|
|
isSafe :: [(Int, [Int])] -> [Int] -> Bool
|
|
isSafe rules = fst . foldl isSafe' (True, [])
|
|
where
|
|
isSafe' (False, prev) _ = (False, prev)
|
|
isSafe' (True, prev) a = (fromMaybe True $ not . any (`elem` prev) <$> lookup a rules, a:prev)
|
|
|
|
part1 :: ([(Int, [Int])], [[Int]]) -> (Int, [[Int]])
|
|
part1 (rules, pages) = first (sum . map takeMiddle) $ partition (isSafe rules) pages
|
|
|
|
part2 :: ([(Int, [Int])], [[Int]]) -> [[Int]] -> Int
|
|
part2 (rules, _) = sum . map (takeMiddle . reorder)
|
|
where
|
|
getPosM rules = memoise $ \values n ->
|
|
let ns = fromMaybe [] $ lookup n rules in
|
|
if null ns
|
|
then (0, values)
|
|
else
|
|
let (ns', values') = memoMap (getPosM rules) values ns in
|
|
(maximum ns' + 1, values')
|
|
|
|
reorder ns =
|
|
let rules' = map (second $ filter (`elem` ns)) $ filter ((`elem` ns) . fst) rules in
|
|
map snd $ sort $ zip (unmemo (memoMap $ getPosM rules') ns) ns
|
|
|
|
main :: IO ()
|
|
main = aocMain' parseFile part1 part2 |