🏡 index : ~doyle/aoc.git

f471b8b86fb78499870b911cfa853b52259e4aa7 [patch]

665c7b8b83205b26612d8f77765499dd5714921c

d23c210e63a139a4a70d02d0bd0be48159174e16

f471b8b86fb78499870b911cfa853b52259e4aa7.tar.gz

Add day 18

Diff

 aoc.hs     |  9 +++++++++
 2023/10.hs | 10 +---------
 2023/18.hs | 62 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 72 insertions(+), 9 deletions(-)

diff --git a/aoc.hs b/aoc.hs
index 551e349..1474b56 100644
--- a/aoc.hs
+++ a/aoc.hs
@@ -57,3 +57,12 @@
    multiChoiceGridTileChar (Just True) = 'O'
    multiChoiceGridTileChar (Just False) = '#'
    multiChoiceGridTileChar Nothing = '.'

-- calculates the area for a polygon described by the set of
-- verticies using the shoelace formula
shoelace :: [(Int, Int)] -> Double
shoelace vertices =

  let pairs = zip vertices $ tail vertices
      sumProd (x1, y1) (x2, y2) = x1 * y2 - x2 * y1
   in fromIntegral (abs . sum $ zipWith sumProd vertices (tail vertices)) / 2

diff --git a/2023/10.hs b/2023/10.hs
index 39d22ba..969bef7 100755
--- a/2023/10.hs
+++ a/2023/10.hs
@@ -1,7 +1,7 @@
#!/usr/bin/env nix-shell
#!nix-shell --pure -i "runghc -- -i../" -p "haskellPackages.ghcWithPackages (pkgs: with pkgs; [ ])"

import Aoc (readAndParseStdin)
import Aoc (readAndParseStdin, shoelace)
import Data.List
import Data.Maybe (listToMaybe)
import qualified Data.Set as Set
@@ -45,14 +45,6 @@
-- use pick's theorem to find the interior lattice points
picksTheorem :: Double -> Int -> Double
picksTheorem area boundaryPoints = area - (fromIntegral boundaryPoints / 2) + 1

-- calculates the area for the polygon described by the set of
-- verticies using the shoelace formula
shoelace :: [(Int, Int)] -> Double
shoelace vertices =

  let pairs = zip vertices $ tail vertices
      sumProd (x1, y1) (x2, y2) = x1 * y2 - x2 * y1
   in fromIntegral (abs . sum $ zipWith sumProd vertices (tail vertices)) / 2

-- builds the list of directions that forms the pipe loop
buildPipeLoop :: [[Tile]] -> [Direction]
diff --git a/2023/18.hs b/2023/18.hs
new file mode 100755
index 0000000..1b40680 100755
--- /dev/null
+++ a/2023/18.hs
@@ -1,0 +1,62 @@
#!/usr/bin/env nix-shell
#!nix-shell --pure -i "runghc -- -i../" -p "haskellPackages.ghcWithPackages (pkgs: with pkgs; [ ])"

import Aoc (readAndParseStdin, shoelace)
import Text.Parsec (char, choice, count, digit, hexDigit, many1, sepBy, spaces, string)
import Text.Parsec.String (Parser)

main = do
  input <- readAndParseStdin parse
  print $ (score . map fst) input
  print $ (score . map snd) input

score :: [(Direction, Int)] -> Int
score input = round $ shoelace (calculateVertices input) + fromIntegral (perimiter input `div` 2) + 1

perimiter :: [(Direction, Int)] -> Int
perimiter = sum . map snd

calculateVertices :: [(Direction, Int)] -> [(Int, Int)]
calculateVertices input = go input 0 0
  where
    go [] hAcc vAcc = []
    go ((d, c) : xs) hAcc vAcc =

      let (newHAcc, newVAcc) = calcAcc d c hAcc vAcc
       in (newHAcc, newVAcc) : go xs newHAcc newVAcc

calcAcc :: Direction -> Int -> Int -> Int -> (Int, Int)
calcAcc U c hAcc vAcc = (hAcc, vAcc - c)
calcAcc D c hAcc vAcc = (hAcc, vAcc + c)
calcAcc L c hAcc vAcc = (hAcc - c, vAcc)
calcAcc R c hAcc vAcc = (hAcc + c, vAcc)

parse :: Parser [((Direction, Int), (Direction, Int))]
parse = parseLine `sepBy` char '\n'

parseLine :: Parser ((Direction, Int), (Direction, Int))
parseLine = do
  p1d <- parseDirection <* spaces
  p1c <- read <$> many1 digit <* spaces
  p2c <- string "(#" *> count 5 hexDigit
  p2d <- parseNumericDirection <* char ')'
  return ((p1d, p1c), (p2d, read ("0x" ++ p2c)))

parseDirection :: Parser Direction
parseDirection =

  choice
    [ U <$ char 'U',
      D <$ char 'D',
      L <$ char 'L',
      R <$ char 'R'
    ]

parseNumericDirection :: Parser Direction
parseNumericDirection =

  choice
    [ U <$ char '3',
      D <$ char '1',
      L <$ char '2',
      R <$ char '0'
    ]

data Direction = U | D | L | R deriving (Show, Enum)