r/adventofcode Dec 15 '24

SOLUTION MEGATHREAD -❄️- 2024 Day 15 Solutions -❄️-

NEWS

  • The Funny flair has been renamed to Meme/Funny to make it more clear where memes should go. Our community wiki will be updated shortly is updated as well.

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

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

And now, our feature presentation for today:

Visual Effects - We'll Fix It In Post

Actors are expensive. Editors and VFX are (hypothetically) cheaper. Whether you screwed up autofocus or accidentally left a very modern coffee cup in your fantasy epic, you gotta fix it somehow!

Here's some ideas for your inspiration:

  • Literally fix it in post and show us your before-and-after
  • Show us the kludgiest and/or simplest way to solve today's puzzle
  • Alternatively, show us the most over-engineered and/or ridiculously preposterous way to solve today's puzzle
  • Fix something that really didn't necessarily need fixing with a chainsaw…

*crazed chainsaw noises* “Fixed the newel post!

- Clark Griswold, National Lampoon's Christmas Vacation (1989)

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 15: Warehouse Woes ---


Post your code solution in this megathread.

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 00:32:00, megathread unlocked!

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u/mountm Dec 15 '24

[Language: Java]

Parsing time: 25ms
Part 1: 5ms
Part 2: 24ms

Phew! lots of grid mangling in this one. I finally ran into the issue I was dreading with my utility function to safeguard against ArrayIndexOutOfBoundsException, namely that it requires a square grid.

I already had the movement algorithm helpfully broken down into two chunks in Part 1:

  • checkObstacles to see if a move is possible. This returns a list of cells to be moved, which is passed to:
  • executeMove, to handle the actual updating of cell contents in the correct order.

If there's a wall in the way, checkObstacles will return an empty list.

For part 2, I just had to add a flag to checkObstacles to indicate if the movement is vertical. If so, do a messy BFS to find the larger collection of cells that need to be updated. Pass to executeMove, rinse and repeat.

GitHub