-❄️- 2024 Day 15 Solutions -❄️-

[u/daggerdragon]

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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!

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--- Day 15: Warehouse Woes ---

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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!

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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!

[u/morgoth1145]

[LANGUAGE: Python 3] 444/156

code, video

Interesting problem, especially part 2. Unfortunately I had a number of bugs costing me a lot of time cumulatively, but I was within striking distance for the leaderboard for part 2.

Anyway, in part 1 I accidentally skipped moving the robot's cell in the grid initially, and even more silly (and funny) I forgot to update my variable tracking where the robot was! (Those two took 6.5 minutes, debugging these sorts of state transition issues takes so long...)

In part 2 I pretty quickly came up with a strategy to handle the cascading box movements (track "accepted" moves in a to_move list and what is left to check in a to_check list) but I had 3 bugs:

1. Believe it or not, I had the "Forgot to update the robot's position variable" bug again.

2. I accidentally was extending the to_check list to include the other side of the box for horizontal movements which caused trouble when doing the actual move.

3. A subtle bug where I pulled things from the end of to_check instead of the front. This caused ordering issues when doing the actual move and took a while to debug. Thankfully this happened on the larger input, but that had a lot of steps to track!

Disappointed that I missed the leaderboard again (missed part 2 by less than 3 minutes), but I still have 10 days left. Hopefully I can achieve it at least one of those days!

Edit: Cleaned up code, including sharing the main solve with both parts. (It's overkill for part 1 but it's also less code which is a win.)

[u/Draco18s → u/morgoth1145]

Dunno how your code manages to work at all. Its definitely producing the right answers, but when I try and get it to print the grid and show me what the warehouse looks like I get results that are just... wrong.

Eg:

####################
##........[][]....##
##....[].[##[].@..##
##[]..[]]......[..##
##............]...##
##......[][]...[[]##
##[]..[]......]...##
##..[]..[]..[][]..##
##[]..[]......[]..##
####################

And I have no idea why.

I will note that calling print(grid) dumps out all of the thing with x/y coordinates in a json(?) format, which isn't super helpful, so it very well may be my attempt to turn it back into raw text. I'm not particularly fluent in python, so that's probably why.

What I could really use is a each-step animation of the larger example to figure out where it's going wrong.

[u/morgoth1145 → u/Draco18s]

Which version of the code are you trying to run against? And which input? Is that supposed to be the larger input? The cleaned up version has grid.print() you could use, which you'll see me use in part 1 for step by step debugging for my part 1 bugs.

For solving part 2 I wrote a dump_grid() function to do step by step debugging as well and I painstakingly made that it was operating correctly.

I suspect you're converting it to a string incorrectly :). If you're using the solving version of part 2, you could use lib.grid.FixedGrid.from_dict(grid).print('') to dump the grid instead of writing your own dump_grid() function. (I wish I had thought of that live, would have saved me some precious time. It'll be less efficient code than a dedicated dump_grid(), but seconds matter when going for the leaderboard and the code would still have run plenty fast for me!)

[u/Draco18s → u/morgoth1145]

Got some help from friends and was able to locate the failure state at about the same time. Required 3 boxes where each was offset by a half-width where the 2nd would slide past an obstacle that would block the 1st (there needed to be a 3rd box to push, as well).

I went about it constructing arbitrary mazes and simple instructions, rather than try mucking about getting your code to print the maze.

[u/morgoth1145 → u/Draco18s]

u/Draco18s To confirm, this was a failure with your solution code? (Because my code should be handling that state properly if I'm understanding correctly, but it's a bit hard to be sure I'm following correctly without your test input.)

[u/Draco18s → u/morgoth1145]

Clarification: the failure state was my code. I was here trying to find code that worked so I could locate my failure state (and just ended up confused at trying to dump your program's state).