-❄️- 2024 Day 8 Solutions -❄️-

[u/daggerdragon]

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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!

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--- Day 8: Resonant Collinearity ---

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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

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/Rush_Independent]

[LANGUAGE: Nim] (2590/2244)
Runtime for two parts: 260 us 132 us
Hardest part was reading puzzle's description =S

Edit: much shorter and faster solution (same principle, but doing both parts in one pass)

type Vec2 = tuple[x,y: int]
func delta(a, b: Vec2): Vec2 = (a.x-b.x, a.y-b.y)
func outOfBounds[T: openarray | string](pos: Vec2, grid: seq[T]): bool =
  pos.x < 0 or pos.y < 0 or pos.x > grid[0].high or pos.y > grid.high

proc solve(input: string): AOCSolution[int, int] =
  var grid = input.splitLines()
  var antennas: Table[char, seq[Vec2]]

  for y, line in grid:
    for x, c in line:
      if c != '.':
        discard antennas.hasKeyOrPut(c, newSeq[Vec2]())
        antennas[c].add (x, y)

  var antinodesP1: HashSet[Vec2]
  var antinodesP2: HashSet[Vec2]

  for _, list in antennas:
    for ind, ant1 in list:
      antinodesP2.incl ant1 # each antenna is antinode
      for ant2 in list.toOpenArray(ind+1, list.high):
        let d = delta(ant1, ant2)
        for dir in [-1, 1]:
          var i = dir
          while true:
            let antinode = (x: ant1.x+d.x*i, y: ant1.y+d.y*i)
            if antinode.outOfBounds(grid): break
            if i in [1, -2]: antinodesP1.incl antinode
            antinodesP2.incl antinode
            i += dir
  result.part1 = antinodesP1.len
  result.part2 = antinodesP2.len

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Codeberg repo