15
submitted 1 week ago* (last edited 1 week ago) by CameronDev@programming.dev to c/advent_of_code@programming.dev

Day 14: Restroom Redoubt

Megathread guidelines

  • Keep top level comments as only solutions, if you want to say something other than a solution put it in a new post. (replies to comments can be whatever)
  • You can send code in code blocks by using three backticks, the code, and then three backticks or use something such as https://topaz.github.io/paste/ if you prefer sending it through a URL

FAQ

you are viewing a single comment's thread
view the rest of the comments
[-] gentooer@programming.dev 3 points 1 week ago* (last edited 1 week ago)

Haskell. For part 2 I just wrote 10000 text files and went through them by hand. I quickly noticed that every 103 seconds, an image started to form, so it didn't take that long to find the tree.

Code

import Data.Maybe
import Text.ParserCombinators.ReadP
import qualified Data.Map.Strict as M

type Coord = (Int, Int)
type Robot = (Coord, Coord)

int :: ReadP Int
int = fmap read $ many1 $ choice $ map char $ '-' : ['0' .. '9']

coord :: ReadP Coord
coord = (,) <$> int <*> (char ',' *> int)

robot :: ReadP Robot
robot = (,) <$> (string "p=" *> coord) <*> (string " v=" *> coord)

robots :: ReadP [Robot]
robots = sepBy robot (char '\n')

simulate :: Coord -> Int -> Robot -> Coord
simulate (x0, y0) t ((x, y), (vx, vy)) =
    ((x + t * vx) `mod` x0, (y + t * vy) `mod` y0)

quadrant :: Coord -> Coord -> Maybe Int
quadrant (x0, y0) (x, y) = case (compare (2*x + 1) x0, compare (2*y + 1) y0) of
    (LT, LT) -> Just 0
    (LT, GT) -> Just 1
    (GT, LT) -> Just 2
    (GT, GT) -> Just 3
    _        -> Nothing

freqs :: (Foldable t, Ord a) => t a -> M.Map a Int
freqs = foldr (\x -> M.insertWith (+) x 1) M.empty

solve :: Coord -> Int -> [Robot] -> Int
solve grid t = product . freqs . catMaybes . map (quadrant grid . simulate grid t)

showGrid :: Coord -> [Coord] -> String
showGrid (x0, y0) cs = unlines
    [ [if (x, y) `M.member` m then '#' else ' ' | x <- [0 .. x0]]
    | let m = M.fromList [(c, ()) | c <- cs]
    , y <- [0 .. y0]
    ]

main :: IO ()
main = do
    rs <- fst . last . readP_to_S robots <$> getContents
    let g = (101, 103)
    print $ solve g 100 rs
    sequence_
        [ writeFile ("tree_" ++ show t) $ showGrid g $ map (simulate g t) rs
        | t <- [0 .. 10000]
        ]

this post was submitted on 14 Dec 2024
15 points (100.0% liked)

Advent Of Code

920 readers
25 users here now

An unofficial home for the advent of code community on programming.dev!

Advent of Code is an annual Advent calendar of small programming puzzles for a variety of skill sets and skill levels that can be solved in any programming language you like.

AoC 2024

Solution Threads

M T W T F S S
1
2 3 4 5 6 7 8
9 10 11 12 13 14 15
16 17 18 19 20 21 22
23 24 25

Rules/Guidelines

Relevant Communities

Relevant Links

Credits

Icon base by Lorc under CC BY 3.0 with modifications to add a gradient

console.log('Hello World')

founded 1 year ago
MODERATORS