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module Main where
import Data.List.Split
import qualified Data.Map as M
import Data.Maybe
run :: [Int] -> Int -> [Int] -> Int
run ls start input = fst $ foldl fn (start, startMap) ls
where startMap = M.fromList $ zip input [1..]
fn (last, seen) i = (i - last', seen')
where last' = fromMaybe i (M.lookup last seen)
seen' = M.insert last i seen
main :: IO ()
main = do
n <- map read . splitOn "," <$> readFile "input/15"
-- holy off-by-one errors
print $ run [8..2020 - 1] 0 n
print $ run [8..30000000 - 1] 0 n
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