One of the reasons I stopped participating was that as the second half of december was approaching I had less and less free time for solving the puzzles. So to me it is also a welcome change, I will try to finish it again this year.
This is fantastic in every way. The hardest part of participating for me was finding more time closer to the holidays as the challenges got harder. Fewer, better challenges, with more space between them and the end of the year is a brilliant solution. So excited and grateful.
Whenever there's a change like this, my gut reaction is to grieve and try to imagine ways that things could be kept the same.
After thinking, "maybe puzzles could be designed by a group instead of an individual and they could share the work," I then thought, "and couldn't an LLM help?"
And with that, I had to remind myself: Advent of Code isn't about there being 25 puzzles, and so maintaining volume at all costs has nothing to do with it.
And aren't we so lucky that it isn't! Aren't we lucky to have had the prior 500+ challenges given as gifts over the years! Aren't we lucky to have a great demonstration of humility and care! Aren't we lucky to have 12 new gifts to look forward to this year!
If he has cut the number of puzzles in half, why not then release a new puzzle every other day? That would make more sense because AoC would still run until Christmas, and it would give people more time per puzzle. Maybe unlock part 2 of each puzzle the day after the puzzle has been posted, so there still something new every day.
I once tried participating, but gave up halfway through because one puzzle per day was just too much time. If it was one puzzle every two days it would be more manageable.
This prompted me to try out claude code on last years... To absolutely no surprise, it looks like the model was trained on advent of code. For the day 2 challenge, I put in this prompt:
for each row in input.txt, identify all the rows where: 1. the columns either all increase or decrease 2. the increase/decrease is >1 and <4. count total # of rows that match this. write a python script
It solved it very quickly. However...
It's solution code included this comment:
Check if a report is safe based on two criteria: │
│ 1. All levels must be either all increasing or all decreasing │
│ 2. Adjacent differences must be between 1 and 3 (inclusive)
This is odd because I never mentioned reports or levels... However the challenge does:
The unusual data (your puzzle input) consists of many reports, one report per line. Each report is a list of numbers called levels that are separated by spaces. For example:
A little sad for me because I've enjoyed the global leaderboard aspect for years but of course my second reaction has to be to take a step back and appreciate all the joy that this one man has given us for all these years.
And he's made it clear from that start that he never intended the global leaderboard to be the point, plus AI the last few years messes it all up. All good things come to an end, and I gotta appreciate the good run that we had, and the voluntary work of one person that gifted it to us.
On the bright side, this will lead to a more relaxed December schedule. I do not compete for the leaderboard, but trying to solve the puzzles on the days they are released (to keep it in the spirit of an advent calendar), and the puzzles towards the end sometimes take me a considerable chunk of the day to solve, which is tricky to combine with the regular schedule, and may be rather stressful (though still a nicer kind of "stressful", as you get on celebrated holidays).
From FAQ: "Why did the number of days per event change? It takes a ton of my free time every year to run Advent of Code, and building the puzzles accounts for the majority of that time. After keeping a consistent schedule for ten years(!), I needed a change. The puzzles still start on December 1st so that the day numbers make sense (Day 1 = Dec 1), and puzzles come out every day (ending mid-December)."
I wonder if it would've felt more natural if the "part 2s" of the puzzles became separate days instead. (Still 12 days worth of puzzles, but spread out across 24 days, with maybe one extra, smaller, easier puzzle for the last day to relax)
Yy usual 5-to-7-day output scramble will now look vastly more competent, ah, well, complete. Not actually be smarter, mind you, but radiate the comforting glow of effort by someone who has their temporal ducks in a suspiciously photogenic row.
Improvement? No. But the illusion of improvement? Practically Nobel-worthy. I'm already enjoying this change.
I've participated in the past, and felt like I always drop off around day 18+ because of holidays etc.
I personally also didn't like when part II of a question felt like a completely new question, instead of a neat extension of the previous one.
I am very happy that this is something that's available to do, for free though. I see advent of code as a good excuse to dabble with a new language, usually with a few people from work.
I love it, starting mid-december a lot of my free time goes into Christmas preparations and at the same time the puzzles went up in difficulty. I never made it past #18 in real time. Not because of the difficulty, I just had to do other things.
Another option would be to add some breaks, maybe a day off every 2 or 3 days.
Big AoC fan these are welcomed changes. I've always started strong but fell off as it was increasingly more difficult to solve puzzles during nighttime. And after you miss one you kinda loose the streak.
This year I'm going to combine it also with mine noaidecember challenge to get a little more dopamine from problem solving.
It is unfortunate, but I can absolutely understand it. Keeping up such open-ended, time-consuming projects year after year while the person doing it changes inevitably – their personal life, habits, job, interests, etc. – must feel like a burden at some point, even if it is out of love and passion (I know that from personal experience with my voluntary work, from which I had to take a break after 10+ years).
I am truly thankful for all of Eric Wastls work on Advent of Code, no matter how much time he can invest and how much puzzles we get. I already look forward to the challenge at the start of autumn and consider what programming language I will choose (this year it’ll be Uiua :)). I am very slow at these puzzles, so I mostly quit at around puzzle 12 anyway, but I learn so much from them and they are a lot of fun.
I love Advent of Code, but my family hates it! Especially the timing in PST! While I understand the challenges of having a global contest, the way this is organized leads to discrimination if, in some countries, you need to be up in the middle of the night.
Although number of puzzles != time investment, selfishly I’m down for this change. As I get older it’s harder to find time to complete them, so I’m hoping this also relieves some of the (artificial) pressure to keep up with daily puzzles by decreasing the time spent per day.
Really appreciate thise changes! Both the reduction in puzzles which means less work, but overall I don’t think it’s going to make the event less fun.
And removing the global leaderboard is good, rather than trying to police how people solve the puzzles just let people have fun on their own boards with people they know.
Make a fun little christmas calendar to bring joy to the people, get turned into a gamified warzone where people use AI and bots to try to get onto the global leaderboards - possibly because getting on them might net you a job at FAANG
I genuinely look forward to Advent of Code every year (whatever that says about me) and next year's one is always on my mind, so naturally I'm somewhat sad about this as the one-puzzle-a-day up to Christmas day just felt very neat, and I liked the mostly gentle initial difficulty curve up to the more 'spiky' questions later.
Having said that, having done a few years now I think the following things end up feeling consistent across years:
The first 10-ish (give or take) days were always simple enough that experienced programmers can likely spit them out during their daily standup. This isn't bad, as I think they're great for newer programmers to get a bit of algorithmic and data structure thinking practice, but they can definitely feel a bit same-y once you've done a few years. This isn't a critique of how AoC was structured, just an observation of how it can feel after you've seen a few years. Having said this, I'm sure I'll miss the gentle warm-up this year.
I wonder what this means for the difficulty curve i.e. the almost-inevitable path-finding question will appear on Day 5 and not Day 15?
I'm sure Eric has thought this through but I wonder if an every-other-day approach (perhaps with a 'softer' puzzle for Christmas day itself) would be popular, as I imagine people balancing a job and/or family while wanting to do this might appreciate having two days for the more challenging later puzzles.
On the other hand, free time for this generally does get more tight as you get closer to the end of the month and the puzzles get more challenging, so this approach does just make a chunk of space for people later in the month, and individuals can choose to keep up with the puzzles on release day if they can or just not worry about it and let things roll over.
Unfortunately, I guess I'll have to actually go and see my family this Christmas instead of ignoring the mandatory visits, which seemed like a fair sacrifice to keep up with calendar ;)
> It takes a ton of my free time every year to run Advent of Code, and building the puzzles accounts for the majority of that time. After keeping a consistent schedule for ten years(!), I needed a change.
Completely fair. As Eric says in some of his presentations on this it takes him about three or four months of his spare time, so this is more than understandable. Props to him for keeping this up consistently with his day job for the last ten years.
> The global leaderboard was one of the largest sources of stress for me, for the infrastructure, and for many users.
I don't mind this so much personally (outside of a morbid curiosity in the really fast participants) although I know people that were really invested in it, but there were some genuine points of contention for people that were interested in the leaderboard:
- The global puzzle unlock time, while explained by Eric himself in his presentations, does make being on the leaderboard impractical for people outside of time zones where the actual release time is friendly for that. For me it's 5am, and the only time I ever came even close (while also being nowhere near...) was when I happened to be up at that time due to insomnia (not caused by AoC).
- It sounded like an infrastructural point of pain as the single global release time coupled with submissions-by-country-size and how keen some of the puzzle solvers are makes for a great initial traffic burst with a long tail (also mentioned on the behind-the-scenes videos).
- It naturally favoured people with an interest in these kinds of puzzles, so the selection bias in the leaderboard is inherently skewed towards a) the subset of people that are choosing to do this out of genuine personal interest and then b) the subset of those that are likely to also be interested in competitive programming-type challenges. This is natural, but I think it does make the leaderboard less relevant for the majority of participants.
- The inevitable contention of the use of 'AI' just to be on the leaderboard
Anyway, I'll just end this with a thank-you to Eric himself for designing and running this consistently for the last ten years as it's something I've come to really enjoy, the community is very lucky to have this, and I hope these changes make it possible for him to continue doing this with lower physical costs to him personally and perhaps lower stress for the participants that just enjoy the puzzles for learning and the rare opportunity to write simple programs to solve problems.
This is completely tangential but as someone who used to be a competitive programmer in the 2010s, I feel like this year marked the end of an era for me.
I don't have time to do regular codeforces/atcoder/leetcode rounds (and the rampant AI cheating is pretty demotivating). So the big annual rituals for me to keep my "competitive programmer" label were: fb hacker cup, google code jam, topcoder TCO, and advent of code. Now besides hacker cup, the rest are dead.
Appreciate it, for me it became this stress inducing xmas calendar. Did it a couple of years and then I stopped because it wasn't fun anymore. Some puzzles were really hard and I took it really personally when I couldn't complete them.
I did exactly half of the puzzles last year, and I think my case is not too uncommon. I am perfectly fine with this, only maybe it would be slightly better if the puzzles came out every two days instead, to ward off the FOMO and give us more time per puzzle?
> If you're still stuck, maybe ask a friend for help, or come back to the puzzle later. You can also ask for hints in the subreddit.
Not sure why this is OK but prompt engineering isn't? If someone wants to test that skillset, let them be instead of asking 'please don't'. Especially given the competitive nature is now optional.
Advent of Code 2025: Number of puzzles reduce from 25 to 12 for the first time
(adventofcode.com)470 points by vismit2000 26 October 2025 | 219 comments
Comments
After thinking, "maybe puzzles could be designed by a group instead of an individual and they could share the work," I then thought, "and couldn't an LLM help?"
And with that, I had to remind myself: Advent of Code isn't about there being 25 puzzles, and so maintaining volume at all costs has nothing to do with it.
And aren't we so lucky that it isn't! Aren't we lucky to have had the prior 500+ challenges given as gifts over the years! Aren't we lucky to have a great demonstration of humility and care! Aren't we lucky to have 12 new gifts to look forward to this year!
Thank you!
I once tried participating, but gave up halfway through because one puzzle per day was just too much time. If it was one puzzle every two days it would be more manageable.
It's solution code included this comment:
This is odd because I never mentioned reports or levels... However the challenge does:And he's made it clear from that start that he never intended the global leaderboard to be the point, plus AI the last few years messes it all up. All good things come to an end, and I gotta appreciate the good run that we had, and the voluntary work of one person that gifted it to us.
That being said, I was worried he'd cancel the entire thing, so this is still good news!
These look like positive changes, a 2x longer event isn't 2x more fun or 2x more satisfying to participate in.
After skipping the past couple of years, I feel like I'm more likely to give it a go again this year.
Yy usual 5-to-7-day output scramble will now look vastly more competent, ah, well, complete. Not actually be smarter, mind you, but radiate the comforting glow of effort by someone who has their temporal ducks in a suspiciously photogenic row.
Improvement? No. But the illusion of improvement? Practically Nobel-worthy. I'm already enjoying this change.
I personally also didn't like when part II of a question felt like a completely new question, instead of a neat extension of the previous one.
I am very happy that this is something that's available to do, for free though. I see advent of code as a good excuse to dabble with a new language, usually with a few people from work.
Another option would be to add some breaks, maybe a day off every 2 or 3 days.
This year I'm going to combine it also with mine noaidecember challenge to get a little more dopamine from problem solving.
I am truly thankful for all of Eric Wastls work on Advent of Code, no matter how much time he can invest and how much puzzles we get. I already look forward to the challenge at the start of autumn and consider what programming language I will choose (this year it’ll be Uiua :)). I am very slow at these puzzles, so I mostly quit at around puzzle 12 anyway, but I learn so much from them and they are a lot of fun.
And removing the global leaderboard is good, rather than trying to police how people solve the puzzles just let people have fun on their own boards with people they know.
Make a fun little christmas calendar to bring joy to the people, get turned into a gamified warzone where people use AI and bots to try to get onto the global leaderboards - possibly because getting on them might net you a job at FAANG
Having said that, having done a few years now I think the following things end up feeling consistent across years:
The first 10-ish (give or take) days were always simple enough that experienced programmers can likely spit them out during their daily standup. This isn't bad, as I think they're great for newer programmers to get a bit of algorithmic and data structure thinking practice, but they can definitely feel a bit same-y once you've done a few years. This isn't a critique of how AoC was structured, just an observation of how it can feel after you've seen a few years. Having said this, I'm sure I'll miss the gentle warm-up this year.
I wonder what this means for the difficulty curve i.e. the almost-inevitable path-finding question will appear on Day 5 and not Day 15?
I'm sure Eric has thought this through but I wonder if an every-other-day approach (perhaps with a 'softer' puzzle for Christmas day itself) would be popular, as I imagine people balancing a job and/or family while wanting to do this might appreciate having two days for the more challenging later puzzles.
On the other hand, free time for this generally does get more tight as you get closer to the end of the month and the puzzles get more challenging, so this approach does just make a chunk of space for people later in the month, and individuals can choose to keep up with the puzzles on release day if they can or just not worry about it and let things roll over.
Unfortunately, I guess I'll have to actually go and see my family this Christmas instead of ignoring the mandatory visits, which seemed like a fair sacrifice to keep up with calendar ;)
> It takes a ton of my free time every year to run Advent of Code, and building the puzzles accounts for the majority of that time. After keeping a consistent schedule for ten years(!), I needed a change.
Completely fair. As Eric says in some of his presentations on this it takes him about three or four months of his spare time, so this is more than understandable. Props to him for keeping this up consistently with his day job for the last ten years.
> The global leaderboard was one of the largest sources of stress for me, for the infrastructure, and for many users.
I don't mind this so much personally (outside of a morbid curiosity in the really fast participants) although I know people that were really invested in it, but there were some genuine points of contention for people that were interested in the leaderboard:
- The global puzzle unlock time, while explained by Eric himself in his presentations, does make being on the leaderboard impractical for people outside of time zones where the actual release time is friendly for that. For me it's 5am, and the only time I ever came even close (while also being nowhere near...) was when I happened to be up at that time due to insomnia (not caused by AoC).
- It sounded like an infrastructural point of pain as the single global release time coupled with submissions-by-country-size and how keen some of the puzzle solvers are makes for a great initial traffic burst with a long tail (also mentioned on the behind-the-scenes videos).
- It naturally favoured people with an interest in these kinds of puzzles, so the selection bias in the leaderboard is inherently skewed towards a) the subset of people that are choosing to do this out of genuine personal interest and then b) the subset of those that are likely to also be interested in competitive programming-type challenges. This is natural, but I think it does make the leaderboard less relevant for the majority of participants.
- The inevitable contention of the use of 'AI' just to be on the leaderboard
Anyway, I'll just end this with a thank-you to Eric himself for designing and running this consistently for the last ten years as it's something I've come to really enjoy, the community is very lucky to have this, and I hope these changes make it possible for him to continue doing this with lower physical costs to him personally and perhaps lower stress for the participants that just enjoy the puzzles for learning and the rare opportunity to write simple programs to solve problems.
For interested watchers:
- 'Eric Wastl – Advent of Code: Behind the Scenes' - https://www.youtube.com/watch?v=_oNOTknRTSU
- 'Keynote: Advent of Code, Behind the Scenes - Eric Wastl' - https://www.youtube.com/watch?v=uZ8DcbhojOw
Edit: Typos
I don't have time to do regular codeforces/atcoder/leetcode rounds (and the rampant AI cheating is pretty demotivating). So the big annual rituals for me to keep my "competitive programmer" label were: fb hacker cup, google code jam, topcoder TCO, and advent of code. Now besides hacker cup, the rest are dead.
Sad. :(
Also after day three I fell hopelessly behind. 12 might be fine.
Not sure why this is OK but prompt engineering isn't? If someone wants to test that skillset, let them be instead of asking 'please don't'. Especially given the competitive nature is now optional.
But since this is the first time I’ve been to the site, I’ve never seen it before. Oh my God it’s completely unreadable.
Seems only FF supports alternate stylesheets, so that’s not a useful solution for me.
Shame. I’m not going to fight that hard to read a website. I’m really sorry, readability is just table stakes.
Oh well.