18 lines
567 B
Haskell
18 lines
567 B
Haskell
import AoC
|
|
|
|
import Data.List
|
|
|
|
pairs :: [a] -> [(a, a)]
|
|
pairs xs = zipWith (,) xs (tail xs)
|
|
|
|
part1 :: [Int] -> Int
|
|
part1 = product . map length . group . sort . map (uncurry $ flip (-)) . pairs
|
|
|
|
numArrangements :: [Int] -> Int
|
|
numArrangements = snd . head . go
|
|
where go xs = foldr (\x acc -> (x, sum . map snd . takeWhile (\(y, _) -> x-y <= 3) $ acc) : acc) [(last xs, 1)] $ init xs
|
|
|
|
main = runAoC (addPhonePort . sortReverse . (0:) . map read . lines) part1 numArrangements
|
|
where addPhonePort (x:xs) = (x+3):x:xs
|
|
sortReverse = sortBy (flip compare)
|