From: Neil Smith Date: Thu, 2 Dec 2021 10:17:28 +0000 (+0000) Subject: Day 2 X-Git-Url: https://git.njae.me.uk/?a=commitdiff_plain;h=f58e7f281200c53dc809be497decdf511efb5c52;p=advent-of-code-21.git Day 2 --- diff --git a/advent-of-code21.cabal b/advent-of-code21.cabal index 54f3668..24e5880 100644 --- a/advent-of-code21.cabal +++ b/advent-of-code21.cabal @@ -84,4 +84,9 @@ executable advent01 -- other-extensions: -- build-depends: base >=4.13 && < 4.15 -- hs-source-dirs: - -- default-language: Haskell2010 \ No newline at end of file + -- default-language: Haskell2010 + +executable advent02 + import: common-extensions, build-directives + main-is: advent02/Main.hs + build-depends: text, attoparsec diff --git a/advent02/Main.hs b/advent02/Main.hs new file mode 100644 index 0000000..360e7e9 --- /dev/null +++ b/advent02/Main.hs @@ -0,0 +1,64 @@ +import Data.Text () +import qualified Data.Text.IO as TIO + +import Data.Attoparsec.Text +import Control.Applicative + +type Course = [Command] +data Command = Forward Int + | Up Int + | Down Int + deriving (Eq, Show) + +data Position = Position Int Int -- forward, depth + deriving (Eq, Show) + +data AimedPosition = AimedPosition Int Int Int -- forward, depth, aim + deriving (Eq, Show) + +main :: IO () +main = + do text <- TIO.readFile "data/advent02.txt" + let course = successfulParse text + print $ part1 course + print $ part2 course + +part1 :: Course -> Int +part1 course = finalH * finalD + where (Position finalH finalD) = followCourse course + +part2 :: Course -> Int +part2 course = finalH * finalD + where (AimedPosition finalH finalD _) = followAimedCourse course + +followCourse :: Course -> Position +followCourse = foldl courseStep (Position 0 0) + +courseStep :: Position -> Command -> Position +courseStep (Position h d) (Forward n) = Position (h + n) d +courseStep (Position h d) (Up n) = Position h (d - n) +courseStep (Position h d) (Down n) = Position h (d + n) + +followAimedCourse :: Course -> AimedPosition +followAimedCourse = foldl courseAimedStep (AimedPosition 0 0 0) + +courseAimedStep :: AimedPosition -> Command -> AimedPosition +courseAimedStep (AimedPosition h d a) (Forward n) = AimedPosition (h + n) (d + a * n) a +courseAimedStep (AimedPosition h d a) (Up n) = AimedPosition h d (a - n) +courseAimedStep (AimedPosition h d a) (Down n) = AimedPosition h d (a + n) + + +-- Parse the input file + +courseP = commandP `sepBy` endOfLine +commandP = forwardP <|> upP <|> downP + +forwardP = Forward <$> ("forward " *> decimal) +upP = Up <$> ("up " *> decimal) +downP = Down <$> ("down " *> decimal) + +-- successfulParse :: Text -> (Integer, [Maybe Integer]) +successfulParse input = + case parseOnly courseP input of + Left _err -> [] -- TIO.putStr $ T.pack $ parseErrorPretty err + Right course -> course diff --git a/data/advent02.txt b/data/advent02.txt new file mode 100644 index 0000000..6c63607 --- /dev/null +++ b/data/advent02.txt @@ -0,0 +1,1000 @@ +forward 8 +down 6 +down 8 +forward 7 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+down 6 +forward 7 +up 2 +down 2 +forward 4 +down 9 +down 8 +forward 2 +forward 2 +down 2 +down 3 +forward 3 +down 1 +forward 8 +down 7 +up 9 +down 4 +down 2 +down 5 +up 7 +down 8 +down 2 +down 4 +down 4 +down 8 +forward 7 +forward 7 +down 8 +up 2 +up 3 +forward 8 +up 1 +down 7 +forward 7 +down 6 +down 8 +up 6 +forward 5 +forward 3 +down 6 +forward 9 +up 4 +up 7 +forward 4 +down 1 +down 8 +down 1 +forward 9 +down 3 +forward 8 +forward 6 +forward 4 +down 9 +forward 3 +up 5 +up 8 +down 9 +down 5 +down 1 +up 8 +forward 8 +up 6 +forward 2 +down 8 +up 4 +up 7 +forward 7 +forward 5 +forward 9 +forward 2 +up 4 +down 9 +forward 7 +down 6 +down 6 +forward 7 +down 5 +up 6 +down 9 +forward 3 \ No newline at end of file diff --git a/problems/day02.html b/problems/day02.html new file mode 100644 index 0000000..499fc0c --- /dev/null +++ b/problems/day02.html @@ -0,0 +1,170 @@ + + + + +Day 2 - Advent of Code 2021 + + + + + + + +

Advent of Code

Neil Smith (AoC++) 4*

   int y=2021;

+ + + +
+ +

--- Day 2: Dive! ---

Now, you need to figure out how to pilot this thing.

+

It seems like the submarine can take a series of commands like forward 1, down 2, or up 3:

+
    +
  • forward X increases the horizontal position by X units.
  • +
  • down X increases the depth by X units.
  • +
  • up X decreases the depth by X units.
  • +
+

Note that since you're on a submarine, down and up affect your depth, and so they have the opposite result of what you might expect.

+

The submarine seems to already have a planned course (your puzzle input). You should probably figure out where it's going. For example:

+
forward 5
+down 5
+forward 8
+up 3
+down 8
+forward 2
+
+

Your horizontal position and depth both start at 0. The steps above would then modify them as follows:

+
    +
  • forward 5 adds 5 to your horizontal position, a total of 5.
  • +
  • down 5 adds 5 to your depth, resulting in a value of 5.
  • +
  • forward 8 adds 8 to your horizontal position, a total of 13.
  • +
  • up 3 decreases your depth by 3, resulting in a value of 2.
  • +
  • down 8 adds 8 to your depth, resulting in a value of 10.
  • +
  • forward 2 adds 2 to your horizontal position, a total of 15.
  • +
+

After following these instructions, you would have a horizontal position of 15 and a depth of 10. (Multiplying these together produces 150.)

+

Calculate the horizontal position and depth you would have after following the planned course. What do you get if you multiply your final horizontal position by your final depth?

+
+

Your puzzle answer was 2039912.

--- Part Two ---

Based on your calculations, the planned course doesn't seem to make any sense. You find the submarine manual and discover that the process is actually slightly more complicated.

+

In addition to horizontal position and depth, you'll also need to track a third value, aim, which also starts at 0. The commands also mean something entirely different than you first thought:

+
    +
  • down X increases your aim by X units.
  • +
  • up X decreases your aim by X units.
  • +
  • forward X does two things:
      +
    • It increases your horizontal position by X units.
    • +
    • It increases your depth by your aim multiplied by X.
    • +
  • +
+

Again note that since you're on a submarine, down and up do the opposite of what you might expect: "down" means aiming in the positive direction.

+

Now, the above example does something different:

+
    +
  • forward 5 adds 5 to your horizontal position, a total of 5. Because your aim is 0, your depth does not change.
  • +
  • down 5 adds 5 to your aim, resulting in a value of 5.
  • +
  • forward 8 adds 8 to your horizontal position, a total of 13. Because your aim is 5, your depth increases by 8*5=40.
  • +
  • up 3 decreases your aim by 3, resulting in a value of 2.
  • +
  • down 8 adds 8 to your aim, resulting in a value of 10.
  • +
  • forward 2 adds 2 to your horizontal position, a total of 15. Because your aim is 10, your depth increases by 2*10=20 to a total of 60.
  • +
+

After following these new instructions, you would have a horizontal position of 15 and a depth of 60. (Multiplying these produces 900.)

+

Using this new interpretation of the commands, calculate the horizontal position and depth you would have after following the planned course. What do you get if you multiply your final horizontal position by your final depth?

+
+

Your puzzle answer was 1942068080.

Both parts of this puzzle are complete! They provide two gold stars: **

+

At this point, you should return to your Advent calendar and try another puzzle.

+

If you still want to see it, you can get your puzzle input.

+

You can also this puzzle.

+
+ + + + + + \ No newline at end of file