好像集训队互测马上要开始了，简单在去年文档的基础上更新一下怎样配置自己的题目。
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IOI 2027 国家集训队互测 传题指南
By
Qingyu
"GPT 話你知": Thoses tasks surpassed by LLMs
By
Qingyu
We are publishing a list of QOJ problems for which LLMs, mostly GPT, have found solutions that are significantly faster than the authors’ intended solutions. If you would like to submit additional problems for inclusion in this list, please write an editorial on QOJ in the problem forum, mark it as anonymous, and leave a comment below.
- For some of the tasks, LLMs even found mistakes in author's solution. Those tasks are marked with †.
- For some of the tasks, LLM's improvement is especially beautiful. Those tasks are marked with ★, stating Qingyu's recommendation.
| Task | From | Author's Solution | GPT's Solution | Article |
|---|---|---|---|---|
| ★Ascending Matrix | XXI Open Cup, GP of Tokyo | $O(K^4 + K^2(N + M + K))$ | $O(K^2 \log^2 K + N + M)$ | by GPT-6 Pro |
| Harsh Comments | XXI Open Cup, GP of Tokyo | $O(S (N + M)))$ | $O(N + S \log S + M \log^2 M)$ | by GPT-6 Pro |
| Rikka with Lake | XXI Open Cup, GP of Xiaomi | $O(n^4)$ | $O(n)$ | by GPT-6 Pro |
| Make It Divisible | ICPC Asia Hangzhou Regional 2024 | $O(T \sqrt {V} + n \log (nV) + n d(V))$ | $O(n + V^{1/3} \log V)$ | by GPT-6 Pro |
| †Dreamy Putata | ICPC Asia Hangzhou Regional 2023 | $O(qm^3 \log n)$ | $O(qm^2 \log n)$ | by GPT-6 Pro |
| 序列变换 | Chinese NOI 2025, Day 1 | $O(N^2)$ | $O(N + \log P)$ | by GPT-6 Pro |
| 彩虹树 | Chinese NOI 2026, Day 2 | $O(n^4)$, $O(n^3 \log n)$ | $O(n^2 \log^2 n)$ | by GPT-6 Pro |
| ★Not a work of Idol | CCPC Finals 2024 | $O(4^p \cdot \text{poly} (p) + T p^2 \log_p^2 n)$ | $O(p^5 \binom{3q}{q} + T p^2 \log_p^2 n) < O(2.6^p + T p^2 \log_p^2 n)$ | by GPT-6 Pro |
| ★Under the Epilogue | CCPC Finals 2024 | $O(n^6)$ | $O(n^{\omega(1,2,1) + \varepsilon}) < O(n^{3.251})$ | by GPT-6 Pro |
| Four Kubic Theorem | CCPC Finals 2025 | $O(\sqrt p \log p)$ | $O(\log p)$, $O(\sqrt p)$ | |
| Spirited Away | CCPC Finals 2025 | $O(n \log^2 V)$ | $O(n \log V)$ | by GPT-6 Pro |
| DFS Order 4 | ICPC Asia EC-Final 2023 | $O(n^3)$ | $O(n^2 \log n)$ | by GPT-6 Pro |
| Coloring | ICPC Asia EC-Final 2022 | $O(n^2)$ | $O(n \log n)$ | by GPT-6 Pro |
| 被 EI 加 0 了 | by Elegia | $O(n^3)$ | $O(n^2 \log^2 n)$ | by GPT-6 Pro |
| ★Ball Machine | IOI 2026 Day 1 | $C = 44$ | $C = 28$ | by GPT-6 Pro |
| World Map | IOI 2025 Day 1 | $K \leq 2N$ | $K \leq 1.25N$ | by GPT-6 Pro |
| 氪金手游 | CTS 2019 Day 2 | $O(n^2)$ | $\widetilde O(n^{(\omega+1)/2}) < O(n^{1.69})$ | by GPT-6 Pro |
| 递增树列 | CTT 2019 Day 1 | $O(n^4)$ | $O(n^2 \log n)$ | by GPT-6 Pro |
| 士兵游戏 | CTT 2022 Day 3 | $O\left(\frac{n}{\log^2 n}\right)$ | $O\left(\frac{n^{2/3}}{\log^{1/3} n}\right)$ | by GPT-6 Pro |
| ★欧拉？欧拉！ | CTT 2022 Day 4 | $O(n^5)$ | $O(n^2 \log^2 n)$ | by GPT-6 Pro |
| 三选二 | CTT 2025 Day 1 | $O\left(\sqrt{n \log n}\right)$ | $O\left(\log^{5.71} n\right)$ | by GPT-6 Pro |
| 染色游戏 | ZJOI 2020, Day 2 | $O(n + r^3)$ | $O(n + r^2)$ | by GPT-6 Pro |
| 树 | ZJOI 2022, Day 1 | $O(n^3)$ | $O(n^2 \log^2 n)$ | by GPT-6 Pro |
| 公交线路 | SNOI 2024, Day 2 | $O(n^2)$ | $O(n^{3/2} \log^{3/2} n)$ | by GPT-5.6 high |
| ★染色数组 | Chinese NOI 2023 Provincial Selection | $O(mn^3)$ | $O(mn^2)$ | by GPT-6 Pro |
| 工业系统 | Chinese NOI 2026 Multi-Provincial Selection | $O(n\sqrt{n+m})$ | $O(n \log n + m\log n)$ | by GPT-6 Pro |
| Sushi | JOISC 2016 Day 3 | $O(N \log N + Q \sqrt N \log N)$ | $O(N \log N + Q \log^2 N)$ | by GPT-6 Pro |
| ★最大值 | by Elegia | $O(n \cdot k^{1.5})$ | $O\left(\min\{n^2k,\ n^{11/2}\sqrt k\log(nk)\}\right)$ | by GPT-6 Pro |
| 复读机 | by Elegia | $O(n ^2)$ | $O(n\sqrt{n\log n})$ | by GPT-6 Pro |
| 新年的神谕 | by Kubic in Goodbye Yisi | $O(n^6)$ / $O(n^5)$ | $O(n^4)$ | by GPT-6 Pro |
| Space Station | The 2nd Universal Cup Semifinals | $O(n^3 V)$ | $O(n^2 V \log n)$ | by GPT-6 Pro |
| Exchanging Kubic 2 | The 2nd Universal Cup Semifinals | $O(n^2 V)$ | $O(n^{\omega - 1} V) < O(n^{1.38} V)$ | by GPT-6 Pro |
| ★Quad Kingdoms Chess 2 | The 2nd Universal Cup Finals | $O(nk^4)$ | $O(nk)$ | by GPT-6 Pro |
| Not Another Constructive Problem | The 2nd Universal Cup Finals | $O(n^3)$ | $O(n^{\omega}) < O(n^{2.38})$ | by GPT-6 Pro |
| Dividing Chains | The 2nd Universal Cup Finals | $O(n^3)$ | $O(n^{\omega}) < O(n^{2.38})$ | by GPT-6 Pro |
| 旧试题 | SDOI 2018, Round 2, Day 2 | $O(n^{1.5} \log^3 n)$ | $O(n^{1+o(1)})$ | by GPT-6 Pro |
| Boxes | The 2024 ICPC Asia East Continent Online Contest (I) | $O(n^2)$ | $O(n\log^4 n)$ | by GPT-6 Pro |
1318 杯唐氏小游戏锦标赛（庆祝澳门将计划承办 IOI 2030）
By
Qingyu
大家好！
为了庆祝澳门将要承办 IOI 2030，1318 于 2026 年 9 月 2 日开展了为期一周的 1318 大学习。为了检验大学习的学习成果，QOJ 将举办「1318 杯唐氏小游戏锦标赛」。任何用户都可以使用自己的 QOJ 账号不限次数地参加该比赛。
比赛包括若干个单项选择问题（每个问题可能包含多个小问），满分 100 分。每道问题中，你需要给一段给定的文字中的某个字选出正确的广东话读音。拼音方案采用「香港語言學學會粵語拼音方案」（由香港語言學學會於1993年製訂的粵語羅馬化方案），并参考了香港中文大学提供的广东话審音配詞字庫。题目的难度将根据你答题的情况动态调整。
本场比赛将公开排行榜，所有选手将根据其分数为第一关键字，结束时间为第二关键字进行排名。在比赛结束（2026 年 9 月 13 日 23:59:59）前，排名 top 3 的队伍将获得「不准作弊」奖，其名字将会出现在「不准作弊」纪念碑中。
比赛的地址位于 https://qoj.ac/games 。 期待所有人参加这场比赛！
The 4th Universal Cup Semifinals
By
Qingyu
Hi all!
It has been quite a while since my last post about the Universal Cup, so here is proof that we are still alive and kicking :) We are excited to announce that The 4th Universal Cup Semifinals will take place on October 11th, 2026!
As in previous seasons, the Semifinals will be held online, and top-performing teams will have the opportunity to advance to The 4th Universal Cup Finals, which we hope to hold in 2027.
Starting this season, we are introducing the new contest format: the Semifinals will be 6-hour contests. The idea of extending the contest duration was first discussed before The 3rd Universal Cup Finals, and we would like to use this opportunity to see how well a longer team contest format works for our competition. Based on how the Semifinals go, we will decide whether to adopt a similar format for The 4th Universal Cup Finals.
The draft of the detailed rules can be found here. But if you do not want to go through the full document, here is the TL;DR:
- The contest will be a 6-hour team programming contest with approximately 10–15 problems.
- The contest will start at 10:00 UTC on October 11th, 2026.
- As always, there will be no partial scoring, and the scoreboard will be live.
- The scoreboard will be frozen 4.5 hours after the start of the contest.
- Recordings are required for all teams wishing to qualify for the Finals. We require screen recordings of every workstation used by the team, as well as video recordings of all team members during the contest. These recordings will be used solely to validate contest performance and will not be published or shared with anyone outside the Universal Cup.
- All Universal Cup Contest Rules, including the rules regarding the fair use of AI models, continue to apply.
We look forward to seeing you in the Semifinals!
(And stay tuned for our next blog post about Season 5 soooooon)
Little Cyan Fish are present in Tashkent / 塔什干有青魚出沒
By
Qingyu
⚠️Beware: Giant Cyan Fish in this area! 🐟
I’ll be attending IOI 2026 and arriving in Tashkent in about 8 hours. If you see me around, feel free to say hi, give me a hug, or come chat with me about the latest stories from QOJ and the Universal Cup, especially if I am lucky enough to be available with free time.
In the mean time, don't forget to do the Prediction Game, check the Schedule, or leave anything in comments about what you'd like to say for IOI 2026. Of course, I won’t be able to write or comment on anything, but nobody can stop me from giving you a little cyan fish badge if I managed to get some...😈
Hope everything goes smoothly at this IOI, hope we won’t get boiled by Tashkent’s weather, and I’m looking forward to seeing all of you there~
