It's only going to be 12 problems rather than 24 this year and there isn't going to be a gloabl leaderboard, but I'm still glad we get to take part in this fun Christmas season tradition, and I'm thankful for all those who put in their free time so that we can get to enjoy the problems. It's probably an unpopular stance, but I've never done Advent of Code for the competitive aspect, I've always just enjoyed the puzzles, so as far as I'm concerned nothing was really lost.
Premises:
(i) I love Advent of Code and I'm grateful for its continuing existence in whatever form its creators feel like it's best for themselves and the community;
(ii) none of what follows is a request, let alone a demand, for anything to change;
(iii) what follows is just the opinion of some random guy on the Internet.
I have a lot of experience with competitions (although more on the math side than on the programming side), and I've been involved essentially since I was in high school, as a contestant, coach, problem writer, organizer, moving tables, etc. In my opinion Advent of Code simply isn't a good competition:
- You need to be available for many days in a row for 15 minutes at a very specific time.
- The problems are too easy.
- There is no time/memory check: you can write ooga-booga code and still pass.
- Some problems require weird parsing.
- Some problems are pure implementation challenges.
- The AoC guy loves recursive descent parsers way too much.
- A lot of problems are underspecified (you can make assumptions not in the problem statement).
- Some problems require manual input inspection.
To reiterate once again: I am not saying that any of this needs to change. Many of the things that make Advent of Code a bad competition are what make it an excellent, fun, memorable "Christmas group thing". Coming back every day creates community and gives people time to discuss the problems. Problems being easy and not requiring specific time complexities to be accepted make the event accessible. Problems not being straight algorithmic challenges add welcome variety.
I like doing competitions but Advent of Code has always felt more like a cozy problem solving festival, I never cared too much for the competitive aspect, local or global.
One could probably build a separate service that provides a leaderboard for solution runtimes.
I agree that it’s more of a cozy activity than a hardcore competition, that’s what I appreciate about it most.
Just a random example: https://open.kattis.com/problems/magicallights
But the Kattis website is great. The program runs on their server without you getting to know the input (you just get right/wrong back), so a bit different. But also then gives you memory and time constraints which you for the more difficult problems must find your way out of.
[0] https://www.jerpint.io/blog/2024-12-30-advent-of-code-llms/
The difference when working on larger tasks that require reasoning is night and day.
In theory it would be very interesting to go back and retry the 2024 tasks, but those will likely have ended up in the training data by now...
It's true this was 4 months after AoC 2024 was out, so it may have been trained on the answer, but I think that's way too soon.
Day 3 in 2024 isn't a Math Olympiad tier problem or anything but it seems novel enough, and my prior experience with LLMs were that they were absolutely atrocious at assembler.
I'm just glad they're keeping this going.
Doing things for the fun of it, for curiosity's sake, for the thrill of solving a fun problem - that's very much alive, don't worry!
Maybe just have a cool advent calendar thingy like a digital tree that gains an ornament for each day you complete. Each ornament can be themed for each puzzle.
Of course I hope it goes without saying that the creator(s) can do it however they want and we’re nothing but richer for it existing.
It becomes a race when you start seeing it as a race :) One can just... ignore the leaderboard
Instead, getting gold stars for solving the puzzles is incentive enough, and can be done as a relaxing thing in the morning.
No matter what you do, as the puzzles get harder, you won't solve them in a day (or even a lifetime) if you don't come up with good algorithms/methods/heuristics.
> Having a leaderboard also leaks into the puzzle design.
Even before LLMs I knew it was filled with with results faster then you can blink.
So some of us, from gut feeling the vast majority, it was always just for fun. Usually I spent at least until March to finish as much as I did in every year.
Many people do - well, did - AoC while ignoring the leaderboard.
In the IEEEXTREME university programming competition there are ~10k participating teams.
Our university has a quite strong Competitive Programming program and the best teams usually rank in the top 100. Last year a team ranked 30 and it's wasn't even our strongest team (which didn't participate)
This year none of our teams was able to get in the top 1000. I would estimate close to 99% of the teams in the Top 1000 were using LLMs.
Last year they didn't seem to help much, but this year they rendered the competition pointless.
I've read blogs/seen videos of people who got in the AOC global leaderboard last year without using LLMs, but I think this year it wouldn't be possible at all.
Cheating is rampant anywhere there’s an online competition. The cheaters don’t care about respecting others, they get a thrill out of getting a lot of points against other people who are trying to compete.
Even in the real world, my runner friends always have stories about people getting caught cutting trails and all of the lengths their running organizations have to go through now to catch cheaters because it’s so common.
The thing about cheaters in a large competition is that it doesn’t take many to crowd out the leaderboard, because the leaderboard is where they get selected out. If there are 1000 teams competing and only 1% cheat, that 1% could still fill the top 10.
> Should I use AI to solve Advent of Code puzzles? No. If you send a friend to the gym on your behalf, would you expect to get stronger? Advent of Code puzzles are designed to be interesting for humans to solve - no consideration is made for whether AI can or cannot solve a puzzle. If you want practice prompting an AI, there are almost certainly better exercises elsewhere designed with that in mind.
Imagine the shitshow that gaming would be without any kind of anti-cheat measures, and that's the state of competitive programming.
reminds me of something I read in "I’m a high schooler. AI is demolishing my education." [0,1] emphasis added:
> During my sophomore year, I participated in my school’s debate team. I was excited to have a space outside the classroom where creativity, critical thinking, and intellectual rigor were valued and sharpened. I love the rush of building arguments from scratch. ChatGPT was released back in 2022, when I was a freshman, but the debate team weathered that first year without being overly influenced by the technology—at least as far as I could tell. But soon, AI took hold there as well. Many students avoided the technology and still stand against it, but it was impossible to ignore what we saw at competitions: chatbots being used for research and to construct arguments between rounds.
high school debate used to be an extracurricular thing students could do for fun. now they're using chatbots in order to generate arguments that the students can just regurgitate.
the end state of this seems like a variation on Dead Internet Theory - Team A is arguing the "pro" side of some issue, Team B is arguing the "con" side, but it's just an LLM generating talking points for both sides and the humans acting as mouthpieces. it still looks like a "debate" to an outside observer, but all the critical thinking has been stripped away.
0: https://www.theatlantic.com/technology/archive/2025/09/high-...
High school debate has been ruthless for a long time, even before AI. There has been a rise in the use of techniques designed to abuse the rules and derail arguments for several years. In some regions, debates have become more about teams leveraging the rules and technicalities against their opponents than organically trying to debate a subject.
With products I want actual correctness. And not something thrown away.
(I did a couple of these in college, though we didn't practice outside of competition so we weren't especially good at it.)
I don’t see why competitive debate or programming would be different. (But I understand why a fair global leaderboard for AOC is no longer feasible).
The Regional Finals and World Finals are in a single venue with a very controlled environment. Just like the IOI and other major competitions.
National High School Olympiads have been dealing with bigger issues because there are too many participants in the first few phases, and usually the schools themselves host the exams. There has been rampant cheating. In my country I believe the organization has resorted to manually reviewing all submissions, but I can only see this getting increasingly less effective.
This year the Canadian Computing Competition didn't officially release the final results, which for me is the best solution:
> Normally, official results from the CCC would be released shortly after the contest. For this year’s contest, however, we will not be releasing official results. The reason for this is the significant number of students who violated the CCC Rules. In particular, it is clear that many students submitted code that they did not write themselves, relying instead on forbidden external help. As such, the reliability of “ranking” students would neither be equitable, fair, or accurate.
Available here: [PDF] https://cemc.uwaterloo.ca/sites/default/files/documents/2025...
Online competitions are just hopeless. AtCoder and Codeforces have rules against AI but no way to enforce them. A minimally competent cheater is impossible to detect. Meta Hacker Cup has a long history and is backed by a large company, but had its leaderboard crowded by cheaters this year.
It's sad, but inevitable, that the global leaderboard had to be pulled. It's also understandable that this year is just 12 days, so takes some pressure off.
If you've never done it before, I recommend it. Don't try and "win", just enjoy the problem solving and the whimsy.
- install like this
- initialize a directory with this command
- here are the VSCode extensions (or whatever IDE) that are the bare minimum for the language
- here's the command for running tests
Huge thanks to those involved!
> If you're posting a code repository somewhere, please don't include parts of Advent of Code like the puzzle text or your inputs.
The text I get, but the inputs? Well, I will comply, since I am getting a very nice thing for (almost) free, so it is polite to respect the wishes here, but since I commit the inputs (you know, since I want to be able to run tests) into the repository, it is bit of a shame the repo must be private.
He's also described, over the years, his process of making the inputs. Related to your comment, he tries to make sure that there are no features of some inputs that make the problem especially hard or easy compared to the other inputs. Look at some of the math ones, a few tricks work most of the time (but not every time). Let's say after some processing you get three numbers and the solution is their LCM, that will probably be true of every input, not just coincidental, even if it's not an inherent property of the problem itself.
There has been the odd puzzle where some inputs have allowed simpler solutions than others, but those have stood out.
if we just look at the last three puzzles: day 23 last year, for example, admitted the greedy solution but only for some inputs. greedy clearly shouldn't work (shuffling the vertices in a file that admits it causes it to fail).
I have a solve group that calls it "Advent of Input Roulette" because (back when there was a global leaderboard) you can definitely get a better expected score by just assuming your input is weak in structural ways.
Python is extremely suitable for these kind of problems. C++ is also often used, especially by competitive programmers.
Which "non-mainstream" or even obscure languages are also well suited for AoC? Please list your weapon of choice and a short statement why it's well suited (not why you like it, why it's good for AoC).
- Array languages such as K or Uiua. Why they're good for AoC: Great for showing off, no-one else can read your solution (including yourself a few days later), good for earlier days that might not feel as challenging
- Raw-dogging it by creating a Game Boy ROM in ASM (for the Game Boy's 'Z80-ish' Sharp LR35902). Why it's good for AoC: All of the above, you've got too much free time on your hands
Just kidding, I use Clojure or Python, and you can pry itertools from my cold, dead hands.
This year I've been working on a bytecode compiler for it, which has been a nice challenge. :)
When I want to get on the leaderboard, though, I use Go. I definitely felt a bit handicapped by the extra typing and lack of 'import solution' (compared to Python), but with an ever-growing 'utils' package and Go's fast compile times, you can still be competitive. I am very proud of my 1st place finish on Day 19 2022, and I credit it to Go's execution speed, which made my brute-force-with-heuristics approach just fast enough to be viable.
That was impressive! Do you have a public repo with your language, anywhere?
Example: find the first example for when this "game of life" variant has more than 1000 cells in the "alive" state.
Solution: generate infinite list of all states and iterate over them until you find one with >= 1000 alive cells.
let allStates = iterate nextState beginState # infinite list of consecutive solutions
let solution = head $ dropWhile (\currentState -> numAliveCells currentState < 1000) allStatesBut yeah, if you're looking to solve the puzzle in under a microsecond you probably want something like Rust or C and keep all the data in L1 cache like some people do. If solving it in under a millisecond is still good enough, Haskell is fine.
Scheme is fairly well suited to both general programming, and abstract math, which tends to be a good fit for AoC.
I write most as pure functional/immutable code unless a problem calls for speed. And with extension functions I've made over the years and a small library (like 2d vectors or grid utils) it's quite nice to work with. Like, if I have a 2D list (List<List<E>>), and my 2d vec, like a = IntVec(5,3), I can do myList[a] and get the element due to an operator overload extension on list-lists.
and with my own utils and extension functions added over years of competitive programming (like it's very fluent
Downsides: The debugging situation is pretty bad (hope you like printf debugging), smaller community means smaller package ecosystem and fewer reference solutions to look up if you're stuck or looking for interesting alternative ideas after solving a problem on your own, but there's still quality stuff out there.
Though personally I'm thinking of trying Go this year, just for fun and learning something new.
Edit: also a static type system can save you from a few stupid bugs that you then spend 15 minutes tracking down because you added a "15" to your list without converting it to an int first or something like that.
OCaml is strong too. Stellar type system, fast execution and sane semantics unlike like 99% of all programming languages. If you want to create elegant solutions to problems, it's a good language.
For both, I recommend coming prepared. Set up a scaffold and create a toolbox which matches the typical problems you see in AoC. There's bound to be a 2d grid among the problems, and you need an implementation. If it can handle out-of-bounds access gracefully, things are often much easier, and so on. You don't want to hammer the head against the wall not solving the problem, but solving parsing problems. Having a combinator-parser library already in the project will help, for instance.
Any recommendations for Go? Traditionally I've gone for Python or Clojure with an 'only builtins or things I add myself' approach (e.g. no NetworkX), but I've been keen to try doing a year in Go however was a bit put off by the verbosity of the parsing and not wanting to get caught spending more time futzing with input lines and err.
Naturally later problems get more puzzle-heavy so the ratio of input-handling to puzzle-solving code changes, but it seemed a bit off putting for early days, and while I like a builtins-only approach it seems like the input handling would really benefit from a 'parse don't validate' type approach (goparsec?).
Once you have something which can "load \n seperated numbers into array/slice" you are mostly set for the first few days. Go has verbosity. You can't really get around that.
The key thing in typed languages are to cook up the right data structures. In something without a type system, you can just wing things and work with a mess of dictionaries and lists. But trying to do the same in a typed language is just going to be uphill as you don't have the tools to manipulate the mess.
Historically, the problems has had some inter-linkage. If you built something day 3, then it's often used day 4-6 as well. Hence, you can win by spending a bit more time on elegance at day 3, and that makes the work at day 4-6 easier.
Mind you, if you just want to LLM your way through, then this doesn't matter since generating the same piece of code every day is easier. But obviously, this won't scale.
Yeah, this is essentially it for me. While it might not be a 'type-safe and correct regarding error handling' approach with Python, part of the interest of the AoC puzzles is the ability to approach them as 'almost pure' programs - no files except for puzzle input and output, no awkward areas like date time handling (usually), absolutely zero frameworks required.
> you can just wing things and work with a mess of dictionaries and lists.
Checks previous years type-hinted solutions with map[tuple[int, int], list[int]]
Yeah...
> but all of the AoC problems aren't parsing problems.
I'd say for the first ten years at least the first ten-ish days are 90% parsing and 10% solving ;) But yes, I agree, and maybe I'm worrying over a few extra visible err's in the code that I shouldn't be.
> if you just want to LLM your way through
Totally fair point if I constrain LLM usage to input handling and the things that I already know that I know how to do but don't want to type, although I've always quite liked being able to treat each day as an independent problem with no bootstrapping of any code, no 'custom AoC library', and just the minimal program required to solve the problem.
* The expressive syntax helps keep the solutions short.
* It has extensive standard library with tons of handy methods for AoC style problems: Enumerable#each_cons, Enumerable#each_slice, Array#transpose, Array#permutation, ...
* The bundled "prime" gem (for generating primes, checking primality, and prime factorization) comes in handy for at least a few of problems each year.
* The tools for parsing inputs and string manipulation are a bit more ergonomic than what you get even in Python: first class regular expression syntax, String#scan, String#[], Regexp::union, ...
* You can easily build your solution step-by-step by chaining method calls. I would typically start with `p File.readlines("input.txt")` and keep executing the script after adding each new method call so I can inspect the intermediate results.
So.. a language that you're interested in or like?
Reminds me of "gamers will optimize the fun out of a game"
I'm pretty clojure-curious so might mess around with doing it in that
A lot of the problems involve manipulating sets and maps, which Clojure makes really straightforward.
Things like `partition`, `cycle` or `repeat` have come in so handy when working with segments of lists or the Conway's Game-of-Life type puzzles.
I tried AoC out one year with the Wolfram language, which sounds insane now, but back then it was just a "seemed like the thing to do at the time" and I'm glad I did it.
(post title: "Designing a Programming Language to Speedrun Advent of Code", but starts off "The title is clickbait. I did not design and implement a programming language for the sole or even primary purpose of leaderboarding on Advent of Code. It just turned out that the programming language I was working on fit the task remarkably well.")
https://github.com/taolson/Admiran https://github.com/taolson/advent-of-code
I wrote a bit more about it here https://laszlo.nu/blog/advent-of-code-2024.html
AoC is a great opportunity for exploring languages!
The spatial and functional problem solving makes it easy to reason about how a single cell is calculated. Then simply apply that logic to all cells to come up with the solution.
I think it lends itself very well to the problem set, the language is very expressive, the standard library is extensive, you can solve most things functionally with no state at all. Yet, you can use global state for things like memoization without having to rewrite all your functions so that's nice too.
Most problems are 80%-90% massaging the input with a little data modeling which you might have to rethink for the second part and algorithms used to play a significant role only in the last few days.
That heavily favours languages which make manipulating string effortless and have very permissive data structures like Python dict or JS objects.
I know people who make some arbitrary extra restriction, like “no library at all” which can help to learn the basics of a language.
The downside I see is that suddenly you are solving algorithmic problems, which some times are bot trivial, and at the same time struggling with a new language.
Sure Haskell comes packaged with parser combinators, but a new user having to juggle immutability, IO and monads all at once at the same time will be almost certainly impossible.
Having smaller problems makes it possible to find multiple solutions as well.
One thing I do think would be interesting is to see solution rate per hour block. It'd give an indication of how popular advent of code is across the world.
I'm also surprised there are a few Dutch language sponsors. Do these show up for everyone or is there some kind of region filtering applied to the sponsors shown?
It's kotlin and shik for me this year, probably a bit of both. And no stupid competitions, AoC should be fun.
We (Depot) are sponsoring this year and have a private leaderboard [0]. We’re donating $1k/each for the top five finishers to a charity of their choice.
>What happened to the global leaderboard? The global leaderboard was one of the largest sources of stress for me, for the infrastructure, and for many users. People took things too seriously, going way outside the spirit of the contest; some people even resorted to things like DDoS attacks. Many people incorrectly concluded that they were somehow worse programmers because their own times didn't compare. What started as a fun feature in 2015 became an ever-growing problem, and so, after ten years of Advent of Code, I removed the global leaderboard. (However, I've made it so you can share a read-only view of your private leaderboard. *Please don't use this feature or data to create a "new" global leaderboard.*)
No thanks.
Having done auth myself, I can also understand why auth is being externalised like this. The site was flooded with bots and scrapers long before LLMs gained relevance and adding all the CAPTCHAs and responding to the "why are you blocking my shady CGNAT ISP when I'm one of the good ones" complaints is just not worth it. Let some company with the right expertise deal with all of that bullshit.
I'd wish the site would have more login options, though. It's a tough nut to crack; pick a small, independent oauth login service not under control of a bit tech company and you're basically DDOSing their account creation page for all of December. Pick a big tech company and you're probably not gaining any new users. You can't do decentralized auth because then you're just doing authentication DDOS with extra steps.
If I didn't have a github account, I'd probably go with a throwaway reddit account to take part. Reddit doesn't really do the same type of tracking Twitter tries to do and it's probably the least privacy invasive of the bunch.
while [1]; do kill -9 $((rnd * 100000)); sleep 5; end
On a serious note, I just saw this: https://linuxupskillchallenge.org
And yet I expect the whole leaderboard to be full of AI submissions...
Edit: No leaderboard this year, nice!
There are plenty of programming competitions and hackathons out there. Let this one simply be a celebration of learning and the enjoyment of problem solving.
> The global leaderboard was one of the largest sources of stress for me, for the infrastructure, and for many users. People took things too seriously, going way outside the spirit of the contest; some people even resorted to things like DDoS attacks. Many people incorrectly concluded that they were somehow worse programmers because their own times didn't compare. What started as a fun feature in 2015 became an ever-growing problem, and so, after ten years of Advent of Code, I removed the global leaderboard.
There will be no global leaderboard this year.
Of course, folks may use it to visualise the puzzles but not to solve them.
[1] https://web.archive.org/web/20241201070128/https://adventofc...
Although there are now rumours of hidden motors in Tour de France bicycles. So, I guess it's the same.