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Day 20 - replaced custom Property data type with Vector.V3 to avoid having to define vector addition and scalar multiplication myself

This commit is contained in:
Jonathan Chan 2017-12-20 11:45:12 -08:00
parent c3c22a5f8f
commit ddd8e7537d
1 changed files with 15 additions and 17 deletions
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20.hs
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@ -2,35 +2,33 @@ import Data.List.Split (splitOn)
import Data.List (elemIndex, sortOn, groupBy) import Data.List (elemIndex, sortOn, groupBy)
import Data.Monoid ((<>)) import Data.Monoid ((<>))
import Data.Function (on) import Data.Function (on)
import Data.Vector.Class
import Data.Vector.V3
data Property = Property Int Int Int deriving (Eq, Ord)
data Particle = Particle { data Particle = Particle {
position :: Property, position :: Vector3,
velocity :: Property, velocity :: Vector3,
acceleration :: Property acceleration :: Vector3
} }
instance Monoid Property where instance Ord Vector3 where
mempty = Property 0 0 0 Vector3 x1 y1 z1 `compare` Vector3 x2 y2 z2 = compare x1 x2 <> compare y1 y2 <> compare z1 z2
Property x1 y1 z1 `mappend` Property x2 y2 z2 = Property (x1 + x2) (y1 + y2) (z1 + z2)
distance :: Particle -> Int norm :: Vector3 -> Double
distance (Particle (Property x y z) _ _) = abs x + abs y + abs z norm (Vector3 x y z) = abs x + abs y + abs z
updateParticle :: Int -> Particle -> Particle updateParticle :: Double -> Particle -> Particle
updateParticle t (Particle p v a) = updateParticle t (Particle p v a) =
Particle (p <> t *** v <> (t * t `div` 2) *** a) (v <> t *** a) a Particle (p + t *| v + (t * (t + 1) / 2) *| a) (v + t *| a) a
where n *** (Property x y z) = Property (n * x) (n * y) (n * z)
stepParticles :: [Particle] -> [Particle] stepParticles :: [Particle] -> [Particle]
stepParticles particles = stepParticles particles =
concat . filter ((== 1) . length) . groupBy ((==) `on` position) . sortOn position . map step $ particles concat . filter ((== 1) . length) . groupBy ((==) `on` position) . sortOn position . map (updateParticle 1) $ particles
where step (Particle p v a) = Particle (p <> v <> a) (v <> a) a
parseProperty :: String -> Property parseProperty :: String -> Vector3
parseProperty str = parseProperty str =
let x : y : z : [] = map read . splitOn "," . drop 3 . init $ str let x : y : z : [] = map read . splitOn "," . drop 3 . init $ str
in Property x y z in Vector3 x y z
parseLine :: String -> Particle parseLine :: String -> Particle
parseLine str = parseLine str =
@ -40,6 +38,6 @@ parseLine str =
main :: IO () main :: IO ()
main = do main = do
particles <- map parseLine . lines <$> readFile "20.txt" particles <- map parseLine . lines <$> readFile "20.txt"
let distances = map (distance . updateParticle 400) particles let distances = map (norm . position . updateParticle 400) particles
print $ elemIndex (minimum distances) distances print $ elemIndex (minimum distances) distances
print $ length $ iterate stepParticles particles !! 40 print $ length $ iterate stepParticles particles !! 40