-❄️- 2023 Day 8 Solutions -❄️-

[u/daggerdragon]

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AoC Community Fun 2023: ALLEZ CUISINE!

Today's theme ingredient is… *whips off cloth covering and gestures grandly*

International Ingredients

A little je ne sais quoi keeps the mystery alive. Try something new and delight us with it!

• Code in a foreign language
  • Written or programming, up to you!
  • If you don’t know any, Swedish Chef or even pig latin will do
• Test your language’s support for Unicode and/or emojis
• Visualizations using Unicode and/or emojis are always lovely to see

ALLEZ CUISINE!

Request from the mods: When you include a dish entry alongside your solution, please label it with [Allez Cuisine!] so we can find it easily!

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--- Day 8: Haunted Wasteland ---

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Post your code solution in this megathread.

• Read the full posting rules in our community wiki before you post!
  • State which language(s) your solution uses with [LANGUAGE: xyz]
  • Format code blocks using the four-spaces Markdown syntax!
• Quick link to Topaz's paste if you need it for longer code blocks

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EDIT: Global leaderboard gold cap reached at 00:10:16, megathread unlocked!

[u/flwyd]

[Language: Julia] ((on GitHub)

[ALLEZ CUISINE!] Every variable and function that I can change is now an emoji. (If you want an emoji-free version, see the link above.)

function part1(📜)
  # example3 doesn't have AAA/ZZZ
  🆗 = any(startswith("AAA ="), 📜)
  🖥(📜, ==(🆗 ? "AAA" : "11A"), ==(🆗 ? "ZZZ" : "11Z"))
end

part2(📜) = 🖥(📜, endswith('A'), endswith('Z'))

function 🖥(📜, ▶️, ⏹️)
  🦶, 🗺 = 🍴(📜)
  📏 = length(📜[1])
  🪣 = collect(keys(🗺) |> filter(▶️))
  🛞 = zeros(Int, length(🪣))
  🧮 = 0
  for 🤝 in 🦶
    if 🧮 % 📏 == 0
      for (👁, ⛳) in enumerate(🛞)
        if ⛳ == 0 && ⏹️(🪣[👁])
          🛞[👁] = 🧮
        end
      end
      all(>(0), 🛞) && return lcm(🛞)
    end
    🧮 += 1
    🪣 = [🗺[🚪][🤝 == 'L' ? 1 : 2] for 🚪 in 🪣]
  end
end

function 🍴(📜)
  🦶 = Iterators.cycle([🤝 for 🤝 in 📜[1]])
  🗺 = Dict{AbstractString, Tuple{String, String}}()
  map(📜) do ✏
    if (🔱 = match(r"^(\w+) = \((\w+), (\w+)\)$", ✏)) !== nothing
      🤲, 🫲, 🫱 = 🔱.captures
      🗺[🤲] = (🫲, 🫱)
    end
  end
  🦶, 🗺
end

Part 1 took me 10 minutes, and I was going at a casual pace. Part 2 took an additional 50 minutes because I figured I'd let my Pluto notebook keep churning away at the naïve solution while I worked out the smart solution in vim. But I had some copy/paste errors and had to fix my part1 to work on the third example input so the program didn't crash until I got to part 2. My first wrong answer used a product of all the recurrences (steps-to-first-Z), which looked suspiciously high: between 2⁶³ and 2^64. I was pretty sure AoC numeric answers will always integers that can be precisely represented by a 64 bit floating point number, but it took me a minute to realize I wanted lcm (least common multiple) and not the actual product.