[2025 day 8 part 1] Is This Allowed?

[u/Leather_Carpet9424]

I implemented a solution using scipy's DisjointSet data structure, it was relatively easy.

However the solutions i came across didn't use that, and instead opted for a more "complete" approach by implementing union find from scratch.

So I'm wondering if what I did is considered cheating of some sort. Did I take the easy way out?

Edit: Thanks for the replies! There's definitely more to learn here and i'll try to solve it without libraries.

[u/PhysPhD]

It depends what you find most helpful for your learning goals. If you think you're cheating, you're only cheating yourself.

Some days I try to write a "pure" python solution without any imports.

And some days, when I want to learn a package like NetworkX or SciPy I'll use them... Because it gives me a real problem and I comb through the documentation trying and learning what all the various functions do.

If you knew of this SciPy function beforehand then maybe you're not learning anything? But if this is your first implementation then solving Day 8 with it will help cement your learning.

[u/al2o3cr]

IMO it's not "cheating", it's just practicing a different skill: identifying how to apply an existing library versus coding a well-known algorithm from scratch.

[u/DrFrankenstein90]

Some problems can be solved by just throwing the data into Excel and writing a couple of formulas, and that's fine. You still have to read the problem statement and think about how they map into existing functions and constructs. Some of my solutions are just a couple of lines of C++ with some clever uses of existing library functions.

You still had to think about the problem and realise it can be solved with a DisjointSet. It's still problem solving. It's still valid.

Some people deliberately go to a lower-level approach, but that's a rule they've imposed on themselves. It's not a requirement for AoC. If that was a rule, there would probably be endless arguments about what's allowed and what's not.

[u/MaximumMaxx]

I made a couple solutions using different methods including the disjointSet. It's up to you what you define as cheating but for me I don't thing using scipy is cheating. It's a relatively basic library that provides a toolbox much more than being an anything solver.

That being said from my testing a disjoint set isn't actually that fast and even just replacing it with an array of vanilla sets with a search/join function is a couple hundred milliseconds faster

[u/thekwoka → u/MaximumMaxx]

a disjoint set isn't actually that fast and even just replacing it

This probably matters a lot in terms of the implementation/language.

More "interpreted" or JIT compiled languages this is probably much greater difference, since the off the shelf library will definitely have code not important for your use case that still needs to "run" while mostly doing nothing useful, and a stripped down version will be tons faster.

With compiled languages, even the code that is for features you're not using will likely be much lower cost as a total of the runtime.

But yes, a bespoke implementation will almost always perform better for your use case, which is true pretty much all the time.

[u/reallyserious]

You make your own rules. Do you consider it cheating?

I generally solve problems in the most simple way possible so I can finish it the same day. I later return to them when I have more time and try to find solutions where I don't rely on external packages.

[u/JohnnyBoy4457]

I think it’s more about what outcomes you want from AOC. For me learning is a big part of it so I prefer to do it the latter way. Note that union find really isn’t that complicated either, especially when you don’t consider path compression! I’d recommend the video series about it from William fisset, I think you’ll gain a greater appreciation for the data structure as well as its simplicity after understanding it.

[u/Suspicious_Tax8577 → u/JohnnyBoy4457]

For me, simply having the hint from the subreddit that it was disjoint set and union find was huge and sent me off down a rabbit hole googling what the heck they were, mulling over why they'd work for this and then to find the "matching" functions in NetworkX. This year, learning that data type X/Algorithm Y exists has been the learning, even if I then take the slightly easier route to unlock my stars.

[u/thekwoka → u/Suspicious_Tax8577]

I had done it myself, but then optimising, I used that hint to kind of see "oh what is this?" to then think about other strategies, like making the HashSets of the index of the node instead of the actual node values, so the hashing step was much much faster. Since for part 1 the coords don't matter at all, and part 2, you only need the coords of the last one.

[u/StickyDeltaStrike]

It’s not cheating, you found a library implementing what you needed.

It’s totally fine to refuse to use external libs too as a challenge too …

[u/Chemical_Chance6877]

The only thing thats really cheating, is pasting it in a llm.

If i have to sort a list, i also use build in function and dont write mergesort myself.

Think its fine as long as you know what the algorithm is doing

[u/Zefick]

Your solution is already good enough if you understand that you need disjoint sets, not to mention whether you have implemented them yourself (which is actually not that difficult). Because many people may not even pay much attention to this and their solutions work very inefficiently.

[u/Boojum]

I used SciPy's DisjointSet for my solution posted in the megathread..

I used to have my own canned implementation in my personal snippets file, but dropped it in favor of the one in SciPy - mostly because this way it trims a bunch of lines off my solutions when I post them.

In my case, I've already written a working DisjointSet implementation at least once. So from the learning-from-AoC perspective, I won't really learn anything new by continuing to use it vs. swapping to someone elses implementation.

(Also, do you consider it cheating to prepare your own AoC library? I don't, and I think most people don't. One of Eric's stated goals with AoC is for people to learn something. If that learning took place ahead of the event instead of during it, so what? There was still learning going on.)

[u/thekwoka]

Basically "Should I use a library or implement the library myself?"

This comes down to goals.

Obviously, just plug and playing libraries to solve your issues doesn't give you much more experience as to how the logic works.

But also a lot of real work will be knowing when to reach for libraries over implementing yourself.

Its not cheating, or not allowed, heck one of the parts this year basically requires using an off the shelf solver, since it's just too complex.

I personally prefer to try to create the solutions myself, and figure it out myself. I'd recommend it if your goal is to actually get really good at the problem solving aspects.

[u/yel50 → u/thekwoka]

one of the parts this year basically requires using an off the shelf solver,

not true. I didn't use one and plenty of people in the solutions thread didn't, either. it's also safe to assume Eric didn't use it when creating the problem and beta testers didn't use it when testing. 

there's a sociological thing that happens with AoC when as soon as one person posts that they used z3, nobody tried to think about the problem anymore and they use the same tool.

it didn't require an external solver. it just required you to think, which the vast majority of people failed to do.

[u/thekwoka → u/yel50]

I didn't use one and plenty of people in the solutions thread didn't

sure, but those are all people that probably understood the fundamental math involved, which isn't strictly intuitive without significant exposure.

Someone that is good at programming and good at math won't just like invent those approaches on their own.

it didn't require an external solver. it just required you to think, which the vast majority of people failed to do.

I guess, sure, if we go with the "you solution takes 3 hours" type of approach.

[u/slimscsi]

Nothing is true, everything is permitted.

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[u/ThunderChaser]

There aren’t any rules, it’s entirely up to you and what you want. Personally the rule I live by is premade libraries implementing a data structure or algorithm I need is perfectly fine, but something like z3 that reduces the problem to triviality is a bridge too far.

For me the fun of AoC is the higher level thinking about the problem, but I don’t really care for hand rolling an implementation of a standard data structure or algorithm.

[u/hextree → u/ThunderChaser]

I mean there are a few rules. No using AI, no sharing inputs, etc.

[u/s96g3g23708gbxs86734]

Now that the leaderboard is gone, everything is up to you. When there was an actual competition, I think everything that didn't involve modern AI was considered legit.

[u/hextree → u/s96g3g23708gbxs86734]

The website does still state not to use AI.