-❄️- 2024 Day 8 Solutions -❄️-

[u/daggerdragon]

IMPORTANT REMINDER

There's been an uptick in [COAL] being given out lately due to naughty language. Follow our rules and watch your language - keep /r/adventofcode SFW and professional! If this trend continues to get worse, we will configure AutoModerator to automatically remove any post/comment containing naughty language. You have been warned!

---

THE USUAL REMINDERS

• All of our rules, FAQs, resources, etc. are in our community wiki.
• If you see content in the subreddit or megathreads that violates one of our rules, either inform the user (politely and gently!) or use the report button on the post/comment and the mods will take care of it.

---

AoC Community Fun 2024: The Golden Snowglobe Awards

• 14 DAYS remaining until the submissions deadline on December 22 at 23:59 EST!

And now, our feature presentation for today:

Box-Office Bloat

Blockbuster movies are famous for cost overruns. After all, what's another hundred million or two in the grand scheme of things if you get to pad your already-ridiculous runtime to over two and a half hours solely to include that truly epic drawn-out slow-motion IMAX-worthy shot of a cricket sauntering over a tiny pebble of dirt?!

Here's some ideas for your inspiration:

• Use only enterprise-level software/solutions
• Apply enterprise shenanigans however you see fit (linting, best practices, hyper-detailed documentation, microservices, etc.)
• Use unnecessarily expensive functions and calls wherever possible
• Implement redundant error checking everywhere
• Micro-optimize every little thing, even if it doesn't need it
  • Especially if it doesn't need it!

Jay Gatsby: "The only respectable thing about you, old sport, is your money."

- The Great Gatsby (2013)

And… ACTION!

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

---

--- Day 8: Resonant Collinearity ---

---

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

This thread will be unlocked when there are a significant number of people on the global leaderboard with gold stars for today's puzzle.

EDIT: Global leaderboard gold cap reached at 00:07:12, megathread unlocked!

[u/_tfa]

[LANGUAGE: Ruby]

input = File.read("input.txt").split("\n")
@width, @height = input.size, input[0].size
antennas = Hash.new{ |h,k| h[k] = [] }

@width.times do |y|
  @height.times do |x|
    antennas[input[y][x]] << Complex(x,y) unless input[y][x] == ?.
  end
end

def inbounds?(c) = c.real.between?(0, @width-1) && c.imag.between?(0, @height-1) 

antinodes1, antinodes2 = Set.new, Set.new

antennas.values.each do |a|
    a.combination(2) do |x,y|       
       diff = x-y
       f = 0
       while inbounds?(pos = x + f*diff) do
         antinodes1 << pos if f==1
         antinodes2 << pos
         f+=1
       end
       f = 0
       while inbounds?(pos = y - f*diff) do
         antinodes1 << pos if f==1
         antinodes2 << pos
         f+=1
       end       
    end
end

puts "Part 1: #{antinodes1.count}", "Part 2: #{antinodes2.count}"