adventofcode-2020/day12/main.hs

#! /usr/bin/env -S"ANSWER=42" nix-shell
#! nix-shell -p ghcid
#! nix-shell -p "haskellPackages.ghcWithPackages (p: with p; [pretty-simple linear])"
#! nix-shell -i "ghcid -c 'ghci' -T main"

{-# OPTIONS_GHC -Wall -Wincomplete-uni-patterns #-}
{-# OPTIONS_GHC -Wno-unused-top-binds -Wno-unused-imports -Wno-type-defaults #-}
{-# OPTIONS_GHC -Wno-unused-matches #-}
{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE DeriveAnyClass #-}

import Debug.Trace (trace, traceShowId, traceShow)
import Text.Pretty.Simple
import Control.Monad
import Linear.V2
import Data.Monoid

exampleData :: [ String ]
exampleData =
  [ "F10"
  , "N3"
  , "F7"
  , "R90"
  , "F11"
  ]



data Ship = Ship { position :: V2 Double, orientation :: V2 Double }
  deriving (Show, Eq, Ord)

-- At first, ship is at (0,0) facing East
ship0 :: Ship
ship0 = Ship (pure 0) (V2 1 0)

-- At first, ship is at (0,0) facing East
ship1 :: Ship
ship1 = Ship (pure 0) (V2 10 1)

-- instance Semigroup Ship
--   where
--     (<>) s1 s2 = Ship (getSum <$> ((Sum <$> (position s1)) <> (Sum <$> (position s2))))
--                       (getSum <$> ((Sum <$> (orientation s1)) <> (Sum <$> (orientation s2))))
--
-- instance Monoid Ship
--   where
--     mempty = Ship (pure 0) (pure 0)

data Instruction  = InsMoveForward !Double
                  | InsMoveNorth !Double
                  | InsMoveSouth !Double
                  | InsMoveEast !Double
                  | InsMoveWest !Double
                  | InsTurnL !Double
                  | InsTurnR !Double
  deriving (Show, Eq, Ord)

parseIns :: String -> Instruction
-- Action N means to move north by the given value.
parseIns ('N':x) = InsMoveNorth (read x)
-- Action S means to move south by the given value.
parseIns ('S':x) = InsMoveSouth (read x)
-- Action E means to move east by the given value.
parseIns ('E':x) = InsMoveEast (read x)
-- Action W means to move west by the given value.
parseIns ('W':x) = InsMoveWest (read x)
-- Action L means to turn left the given number of degrees.
parseIns ('L':x) = InsTurnL (read x)
-- Action R means to turn right the given number of degrees.
parseIns ('R':x) = InsTurnR (read x)
-- Action F means to move forward by the given value in the direction the ship is currently facing.
parseIns ('F':x) = InsMoveForward (read x)
parseIns e = trace ("Unknown instruction: "<>show e) undefined


-- 2*PI rad = 360 deg
-- 1 rad = 180/PI deg
-- PI/180 rad = 1 deg

runIns1 :: Ship -> Instruction -> Ship
runIns1 s (InsMoveForward n) = s { position = (position s) + (pure n) * (orientation s) }
runIns1 s (InsMoveNorth n)   = s { position = (position s) + (pure n) * V2 0     1    }
runIns1 s (InsMoveSouth n)   = s { position = (position s) + (pure n) * V2 0     (-1) }
runIns1 s (InsMoveEast n)    = s { position = (position s) + (pure n) * V2 1     0    }
runIns1 s (InsMoveWest n)    = s { position = (position s) + (pure n) * V2 (-1)  0    }
runIns1 s (InsTurnL n)       = s { orientation = angle ((unangle (orientation s)) + n * pi / 180) }
runIns1 s (InsTurnR n)       = s { orientation = angle ((unangle (orientation s)) - n * pi / 180) }

manhattanV2 :: (Num a) => V2 a -> a
manhattanV2 (V2 x y) = (abs x) + (abs y)

solvePart1 :: [String] -> Double
solvePart1 = manhattanV2 . position . foldl runIns1 ship0 . map parseIns



--------------------------------------------------------------------------------

runIns2 :: Ship -> Instruction -> Ship
runIns2 s (InsMoveForward n) = s { position = (position s) + (pure n) * (orientation s) }
runIns2 s (InsMoveNorth n)   = s { orientation = (orientation s) + V2 0     n     }
runIns2 s (InsMoveSouth n)   = s { orientation = (orientation s) + V2 0     (-n)  }
runIns2 s (InsMoveEast n)    = s { orientation = (orientation s) + V2 n     0     }
runIns2 s (InsMoveWest n)    = s { orientation = (orientation s) + V2 (-n)  0     }
runIns2 s (InsTurnL n)       = s { orientation = rotV2By (orientation s) n }
runIns2 s (InsTurnR n)       = s { orientation = rotV2By (orientation s) (-n) }

rotV2By :: (Num a, Floating a) => V2 a -> a -> V2 a
rotV2By (V2 x1 y1) n = V2 x y
  where
    x = cos a * x1 - sin a * y1
    y = sin a * x1 + cos a * y1
    a = n * pi / 180

solvePart2 :: [String] -> Double
solvePart2 = manhattanV2 . position . foldl runIns2 ship1 . map parseIns

main :: IO ()
main = do
  input <- lines <$> readFile "day12/input"
  putStrLn ":: Tests"
  pPrint exampleData
  pPrint $ map parseIns exampleData
  pPrint $ angle (90 * pi / 180)
  putStrLn ":: Day 12 - Part 1"
  pPrint $ solvePart1 exampleData
  pPrint $ solvePart1 input
  putStrLn ":: Day 12 - Part 2"
  pPrint $ solvePart2 exampleData
  pPrint $ solvePart2 input