lwhjp, 5 months ago (edited 5 months ago)

Haskell

This problem has a nice closed form solution, but brute force also works.

(My keyboard broke during part two. Yet another day off the bottom of the leaderboard…)

<span style="color:#323232;">import Control.Monad
</span><span style="color:#323232;">import Data.Bifunctor
</span><span style="color:#323232;">import Data.List
</span><span style="color:#323232;">
</span><span style="color:#323232;">readInput :: String -> [(Int, Int)]
</span><span style="color:#323232;">readInput = map ([t, d] -> (read t, read d)) . tail . transpose . map words . lines
</span><span style="color:#323232;">
</span><span style="color:#323232;">-- Quadratic formula
</span><span style="color:#323232;">wins :: (Int, Int) -> Int
</span><span style="color:#323232;">wins (t, d) =
</span><span style="color:#323232;">  let c = fromIntegral t / 2 :: Double
</span><span style="color:#323232;">      h = sqrt (fromIntegral $ t * t - 4 * d) / 2
</span><span style="color:#323232;">   in ceiling (c + h) - floor (c - h) - 1
</span><span style="color:#323232;">
</span><span style="color:#323232;">main = do
</span><span style="color:#323232;">  input <- readInput <$> readFile "input06"
</span><span style="color:#323232;">  print $ product . map wins $ input
</span><span style="color:#323232;">  print $ wins . join bimap (read . concatMap show) . unzip $ input
</span>