import Aoc ( aocMain )

parseFile :: [String] -> [[Int]]
parseFile = map (map read . words)

part1 :: [[Int]] -> Int
part1 reports =
    length $ filter isSafe $ map differences reports
    where
        differences xs = zipWith (-) xs (tail xs)
        isGradual dx = 1 <= abs dx && abs dx <= 3
        isSafe dxs = all isGradual dxs && (all (<0) dxs || all (>0) dxs)

part2 :: [[Int]] -> Int
part2 reports = 
    length $ filter isSafe $ map remove1 reports
    where
        remove n xs = let (front, back) = splitAt n xs in front ++ tail back
        remove1 report = map (`remove` report) [0..length report-1]
        isSafe = (>0) . part1

main :: IO ()
main = aocMain parseFile part1 part2