04:45

04:30

04:00

03:05

![ ]()

Scoreboard at 02:20

Problem 5 has been conquered by I_love_Khanh_Dan at 01:13

Problem 4 has been conquered by i_love_huyhau6a2 at 00:50

04:45

04:30

Scoreboard at 04:00. Two more ACs of P1 has been made

Problem 2 has been conquered by SmuggingSpon at 03:35. All three Day1 problems has been conquered by at least one contestant

Scoreboard at 03:00

Problem 3 has been conquered after 02:45 of very low activity from I_love_Khanh_Dan

Problem 1 has been conquered at 02:23

Scoreboard at 02:00

Scoreboard at 02:00

holy shti

ahihi1234 just went from 0 to 80 in less than a minute

Scoreboard at 01:00

yes

already updated

Auto comment: topic has been updated by Down_bad_4_haiender288 (previous revision, new revision, compare).

Auto comment: topic has been updated by Down_bad_4_haiender288 (previous revision, new revision, compare).

ok noted

we do operate on our own schedule after all

Da 36 lai con 67

Scam vua thoi em yeu

For the collective consciousness to laugh together at the

• Pretty decent and challenging problems

• "oh GOD they are copy pasting research papers again" problem

• some impossible bullshit around as bullshit as those 0ACs intentionally bullshit JOISC or the average CTSC problem

Same situation with the Kims, I suppose

Personal horse betting for top 6 after 2 competition days, purely based on familiarity with no logical backing whatsoever:

1st: I_love_Khanh_Dan

2nd: i_love_huyhau6a2

3rd: ahihi1234

4th: EtherStrike

5th: modwwe

6th: SmuggingSpon

Note that this year's competition for IOI would be especially rough. Normally, we'd only have 1-2 especially dominating candidates that most likely will go to IOI should things not go wrong (examples of "things goes wrong" includes APIO24's Magic Shitshow). The rest are wildcards that may lucksack and win the competition by surprise, or flopped like hell for no particular reason whatsoever.

However, this year around, out of the 38 contestants, the lineup consists of the following highly notable individuals:

• Nguyen Phu Nhan (SmuggingSpon): IOAI25 Gold Medalist

• Nguyen Huu Tuan (ahihi1234): IOI24 Silver Medalist, IOAI25 Gold Medalist, first Vietnamese 10th grader to qualify for IOI

• Nguyen Viet Trung Nhan (nathan4690): IOAI25 Gold Medalist

• Nguyen Khanh Phuc (I_love_Khanh_Dan): Youngest Vietnamese GM + a bunch of other insane shit never done before

• Dang Huy Hau (i_love_huyhau6a2): IOI25 Silver Medalist, second Vietnamese 10th grader to qualify for IOI

• Nguyen Bui Duc Dung (EtherStrike): IOI25 Silver Medalist

• Thieu Nguyen Huy (tnhwe): #3 in Vietnamese TST25

• Nguyen Xuan Chi Thanh (Thanhs): #4 in Vietnamese TST25

• Nguyen Huy Phong (modwwe): APIO25 Bronze Medalist

.......and at least 20 other wildcards.

This will be the biggest bloodbath for IOI in the VNOI community in the past 15 years, and I am...very much hyped for it

Auto comment: topic has been updated by Down_bad_4_haiender288 (previous revision, new revision, compare).

Congratulations Kevin114514 for being the first 10th grader Chinese IOIer. Nobody could've seen this coming, definitely

Tbh proposing literal random bullshit to the IOI is not even that bad of an idea at this point. After Mosaic and the other incidents related to "easy" tasks as of late, proposing literally anything seems to work, as long as it's easy.

At least we have our glorious king FelixMP and the Yoneda brothers hard carrying the "simpler" tasks. Dear god.

Some things to add on this:

1) On the old IOI website (ioi.te.lv), there are, if I recall correctly, 3-5 papers on approaches to problemsetting, and if you broaden the scope to "schools of thought for problemsetting" there are quite a handful of them over there.

2) On problemsetting approaches:

• Problems created from natural observation are bound to be fairly practical and are much more likely to possess degrees of reusability. Highly likely for cool stuffs to appear as well.

• Problems created by "just cooking old problems, duh" might be unoriginal and all, but at least their difficulty are more or less controlled (i.e if an algorithm is used for the original, it is expected that the v2.0 only applies a slightly more difficult/different version of the thing"

.....unless it is UCS (IOI24 P4). Author intended to propose it for some small regional competition and it turned out to be an unfathomable monstrority that took 6 months to solve and scammed some 30 contestants into banging their head into the monster for 3 hours instead. It do be like that sometimes.

...if it is intended to be the "hard" task, then probably. If it's the anti-AC problem, every ceiling is removed (see: Migrations' 250 lines of if-else)

Nope, problem even easier than 2021's DNA it is!

(Proposed something even easier than 2010's Cluedo. yuantiji.ac yields nothing, so it is more original than 2019's Shoes. Yay!)

Tracking changes while iterating from left-right: by caseworking all 4 cases of 2 adjacent ones, you'll notice that the amount of seen wizards can change by at most 1 => if it's >=2, it is bullshit

Basically, for the other situations: If the amount of seen wizards are the same across the entire array, some simple casework is sufficient (again, just write the case for N=3 and N=4 out).

Otherwise, when the amount of seen wizards differs by at most 1 between 2 adjacent elements, you can identify at least 1 wizard, and from that reconstruct the entire sequence. After that, just slap some prefix sums to check whether the sequence is consistent to the input or not

With everything that has happened, it was definitely for the best that it wasn't shortlisted. Tree/UCS/Message are all unfathomable peaks that should remain in the problemset at all costs....and imagine having to deal with them alongside...this. The poor contestants' brains.....

Well, congratulations for the 2nd IOI takeover in less than 2 years

it is NOT an answer, and actually planning/organizing an IOI takes a lot of time. Apparently we are NOT there yet.

Just my hopeful wishes

Were there any chance Migration was the backup shortlisted task you two had for IOI24?

Congratulations for your 2nd IOI task (Comparing Plants was mad cool as well). Please keep cooking (especially DS tasks)

Road to 2037.

Wdym having Vietnam compete with the world, our glorious Peruvian representative just outdid himself yesterday

Wow, Mr.Tan is certainly arranging things fairly efficiently. A 2nd run in Japan in 10 years is somewhat iffy, but Japan is cool so that's fine

(I recall there were words about multiple....minor logistical issues that snowballed into a bit of unfun things for some contestants. Let's hope that it does NOT happen again)

Will there be a livestream of the closing ceremony like the past few years?

Quick braindead initial impressions of Day2 tasks:

Festivals: Another "simple setting" IOI task. No comment

Migration:

No ACs, only partial scores.

Probably another OO

looks inside

Communication problem.

Yes it is very hard. Probably not the same situation as IOI19's Broken Line where a deterministic polynomial solution exists but people don't bother to do that.

Obstacle for a Llama: M*saic, but good. Actual DS task. Yay. Probably in the same vein with those magical JOISC DS problem.

Given how nice the scoring turned out (well, I certainly don't know whether 50+ ACs plus some 67s and the rest were 39s would be considered nice scoring) for this supposed "easy" task.....and M*saic got in, it is a total shame. Should've been shortlisted for IOI24 tbh

Congratulations for your 3rd IOI task. Was it based on the reversed engineered version of 1951D?

Authors, you can come out now. Please. Since it appears the tasks are all very balanced and offered a very good score distribution, we won't jump you.

P4 has been murdered at 00:45, and P6 has been destroyed at 01:50. BreakPlay is making very quick work of the problemset

Problem 4 has been murdered at 00:45

The Day 1 problemset looks weird, I have no idea how to approach P1 and P3. (This time around I didn't even wait for mirrors or even wanted to for that matter, now I'm at a point where OIs are completely out of the question, no need to constraint myself to the competition format). Really cool though.

Difficulty seems really "balanced" in a sense somewhat similar to IOI21 day 1 (with generally low amount of ACs). As for general difficulty benchmark, from statistics, sorted by order:

Partial P3 (at least 72pts) < full P1 < at least 70pts P2 < full P3.

Was completely stumped by P1 despite it supposed to be the "easiest" one to AC. Pretty cool problem (seems like a very messed up, reverse-engineered version of 1951D).

When I was made aware of the mixed format tasks, I totally thought that it was supposed to be following the addition of some small OO subtasks to prevent absolute zeroes from happening....but it turns out that the OO section was actually the last 30pts for the tie-breaker instead. Totally didn't call that. If anything I'd say that this is probably the most innovative (in terms of formating) since, uhhh, 2019's Vision Program (baby's first Machine Building task)? Either way, brand new format is cool, new problem types are appreciated.

(Still can't believe that people haven't thought about such a type of "solving both ways" task before, but ah well. As my brain has been completely fried as of late, I will just proceed to patiently wait for Errichto's explanations tomorrow).

Map is just...cool. Like, wow. Really good problem. Never thought of that. Just...wow. Not "unfathomable peak" level of cool, but still cool regardless.

That's part of the authentic cultural experiences, I guess. Not the best thing that could've happened but certainly something to remain in the local IOI folklore for quite a while

Jesus that was certainly the experience of a lifetime right there

From what it seems, P1 is still the "easiest" in the sense that it's the easiest AC (in comparission to the other 2). Still blindsided by it though tf are you supposed to do with that.

At least it appears that the Day1 problemset is fairly balanced and consistent in terms of difficulty

Now that the 1st competition day has ended, can anyone give out the content of the tasks?

Yeah, I have no idea how our government even arranged those flights...but at least it's free for the contestants, I guess

The last few hours has been pretty boring, but:

• Despite P2 seeming like an OO, it has been conquerred at around 02:45 (by BreakPlay)

.....who also happens to be the first to conquer the Day1 problemset at 03:15. Congratulations

From what it seems, top 30 for day 1 would probably be around at least 250pts. IOI25 might have very high Gold cutoff?

Hour 1 leaderboards:

Generally speaking:

• P1 is the "easy" task, with several ACs already

• P2 looks pretty scary with the 12 subtasks, but 70pts has already been acquired

• P3 got its first 72pts solution around 20 minutes into the contest. Current max is 86, from none other than mr "textsolved the constructive Div1F and won the IMO" himself

This is the point where you should definitely yeet that phone away, we do not need another out-of-the-box 50pts solution again

Edit: nvm im a fucking idiot competition has began

not out yet

Shout out to PeruvianCartel's latest R18 leak. Can't believe he did this in public. Smhmh

Indeed. It has lead to several contestants getting jabaited pretty hard and losing a good chunk of point, severely degrading their well-deserved medal, and for certain contestants, they might've lost more than that.

It is exactly that bad. I mean, most other International Olympiad tasks weren't rejected by almost half the delegations

Holy shit

It appears that IOI25 has officially begun. Or in...15 minutes, according to the schedules, I guess.

Hope that you contestants would not suffer too bad from the jet lag, because a 12h gap is crazy

So it is true, mister "perfect score in IMO with a textsolve for the constructive Div1F" is indeed an IOI contestant

Right now, it seems that most of the contestants are on their last leg — a fairly lengthy transit (for the Vietnamese delegation and most of the other Asian delegations, I presume, one in Brazil).

Seriously, that is some bloodly long travel time right there

Posting this early, because it seems that most countries will be boarding the flights to IOI25 pretty soon.

Apparently the guest fee for this year is pretty cheap (650$ per person, down to 600$ if it is shared, instead of the usual 1500 euros). This might be to compensate the high cost of plane tickets? (From what I do know, plane tickets for the Vietnamese delegation is at around 6500$ per person (on total, for the initial and returning flights), which is...quite a lot)

To a (or several) certain Scientific Committee: Please look at this, and do not the Mosaic

Heard that the problemset has 2 interactives and 1 constructive. What the hell lmao

The prelimary results for APIO25 is out, and so is Vietnam's IOI25 team (it has been since yesterday, but it was advised that no leaking happened before the contest window ended). Congratulations to the following peeps for winning a free week-long vacation on top of some mountains:

1) Le Kien Thanh (steveonalex/alexonsteve/PeruvianCartel): 165.64 + 82.81 + 195 = 443.45 pts (1st time at IOI, 0 attempt left)

2) Dang Huy Hau (i_love_huyhau6a2) : 160.62 + 79.94 + 190 = 430.56 pts (1st time at the IOI, 2 attempts left)

3) Nguyen Bui Duc Dung (Skyan, probably): 95.24 + 91.45 + 236 = 422,69 pts (1st time at the IOI, 1 attempt left)

4) Ninh Quang Thang (thangdz2k7): 127.3 + 65.27 + 145 = 337.67 pts (1st time at the IOI, 0 attempt left)

When is the shortlist supposed to be finalized? Really weird how (apparently) problemsetters haven't heard anything back a week before the task statement distribution date........

Magic (shit)Show

I mean, there's one E Edu Div2 from towards the end of 2023 that was APIO22's Permutations, word for word (with a much easier bound, the "easy" solution for Perm is 120 numbers, while that problem has 200), nd somehow that still got in for whatever reason. I think that there's definitely something wrong (in the sense that yuantiji.ac isn't updated as frequently as it should have, and the coordinators aren't that good at noticing similarities as they should've)

Edit: 1922E

IOI22's Prisoner Challenge

.

The clock is ticking......

dude got @-ed on a daily basis after recent stuffs, lmao

Finalized scoreboard

04:45

04:30

04:15

4 hour, 15 minutes interval from this point on

Scoreboard at 03:00 of Day 2

Scoreboard at 02:38 of day 2

Finalized scoreboard of Day 1

Last 15 minutes

Scoreboard at 04:30

Scoreboard at around 04:20. Last hour, people have subbed their P2 (it is an OO).

2 just got 10 more points in P3, and swapped to #1

4th hour, Updates every 15 minutes from now on

P3 is still more or less untouched

Scoreboard after 3.25h.

No major changes so far.

Scoreboard after 2 hours:

Important changes:

• 3 ACs in P1 now
• Highest score in P2 is now 49.9
• P3 has yet to be dealt with

P1 have been AC-d at around 01:12

Scoreboard at 01:00

(Forgot to add it into the post, but I had to travel very far to make it to the contest venue and cheer for the contestants. This has been my most lengthy detour in 2025 so far)

Some fun historical fact: P2 (Letter Pair Move Game) is a generalized version of the 1st IOI task (in that task, the 2 empty boxes is in the middle)

Worry not, for you are a rythmn gamer. You will be blessed

(And even if you won't, the message straight above is enough of an indication that your thesis defense is everything (for the next step). Good luck.)

The "regardless of any selection results" means that it is (theoretically) possible for #3-6 to become the official IOI team, is my understanding correct?

UCS

Wtf how is your english speaking persona so different from your brainrot speaking persona

Road to IOI25 when?

That's some classic, traditional miswording from my side. I was talking about your win in the 2018 College Students Olympiad in Informatics (roughly/badly translated name).

(that is to say that what I was trying to say is among the lines of "wow jesus christ didn't know that you managed to do those shits 6 years ago" that got lost in horrible shitass expression. (and, once again, if my horrible way of expressing things procced again, this is literally fanboying, NOT dissing or anything slightly negative).That doesn't stray away from the fact that you're literally a borderline genius at base, though, if anything I'm surprised you haven't made it to low-GM just yet.

Btw, yes, I suppose the information is correct, your birthday checks out (down to the exact day and year), your university profile (?) checks out, and your mannerisms/talking style matches what I expect from.....a person in that background. Some intuition/spidey senses told me you're probably no normal person, tried typing your name into the local browser's search bar and....jesus christ)

Jesus christ what an absolute SCAM, bro definitely participated in VOI before, with a friking SC win and bronze ICPC APAC to boot. Come on, man.

(At least now I do know that my sense for detecting weird people haven't failed me even once)

very bad at casework and implementing but basically if n+sqrt(n)< (the smallest perfect square larger than n) it is n+sqrt(n), otherwise n+sqrt(n)+1

took half an hour to implement

i am bad at this

Write down everything, treating each substep as its own task and pretend it's the local MO contest where everything have to be proven (as long as it isn't too obvious)