Qingyu's blog

IOI 2025 China Team Selection — Current Standings
By Qingyu, 3 months ago, In English

Hi, everyone.

The first stage of the IOI 2025 China Team Selection began yesterday. The top 50 participants from the 2024 National Olympiad in Informatics (NOI) will compete for a spot on the Chinese national team for IOI 2025.

The rule of selecting CHN team this year:

  • Homework (10%): also known as mutual tests, where the students were asked to prepare a task (5%), and participate in the contests made by other students (5%)
  • First stage (CTT; 54%; Dec 3, 2024 — Dec 5, 2024): three contests in classic olympiad format, where each contest worthes 18% of the score. Top 30 participants will advance to the final stage.
  • Final stage (CTS; 36%; Jan 20, 2025 — Jan 22, 2025): two contests in classic olympiad format, where each contest worthes 18% of the score.

The current scoreboard can be found here.

Past problems of the China IOI Team Selections can be found here (first stage and final stage). I will upload all the tasks once they can be publicly shared.

  • Update 1: The first stage has been finished. You can find the problems here. The final stage will take place on Jan 20 and Jan 22, 2025.
  • Update 2: All the contests have been finished now. The final scoreboard has been updated.
  • Update 3: Problems from the final round can be found here.
  • Update 4: The CHN team has been announced: Liu Hengxi liuhengxi, Liu Haifeng crazy_sea, Chen Xinyang JoesSR, and Fan Sizhe umbrella-leaf. Congratulations!
  • Vote: I like it
  • +420
  • Vote: I do not like it

»
3 months ago, # |
  Vote: I like it 0 Vote: I do not like it

is there any scoreboard that can be accessed in china?

→ Reply
»
3 months ago, # |
  Vote: I like it +66 Vote: I do not like it

I'm wondering if you can connect the participants with their cf handles.

→ Reply
»
3 months ago, # |
  Vote: I like it +41 Vote: I do not like it

I'm curious, but how is the homework scored (specifically on the part of setting problem)?

→ Reply
  • »
    »
    3 months ago, # ^ |
    ← Rev. 3   Vote: I like it +39 Vote: I do not like it

    Submit any task = 3.2p

    Task is used in mutual tests(I think any competitive programming problem will be used) = 0.6p

    Feedback from participants and coaches(the weirdest part, easy problems are getting better score) = 1.2p

    Participate in mutual tests with >=60p = 0.6p*7=4.2p

    Participate in mutual tests with rank <=20 = 0.16p*5=0.8p

    → Reply
»
3 months ago, # |
  Vote: I like it 0 Vote: I do not like it

is the allegation true that being a top 50 candidate in the NOI is harder than winning gold at the IOI?

→ Reply
  • »
    »
    2 months ago, # ^ |
      Vote: I like it +3 Vote: I do not like it

    I don't know.But as a student from China,I can tell you one thing:China's top 50 players are just as good as international grandmaster.

    → Reply
  • »
    »
    2 months ago, # ^ |
      Vote: I like it +3 Vote: I do not like it

    Some of them are better than international grandmaster.For example,one student from my school called grass8sheep.He ranked 18th in this year's NOI.He is a red coder too,but in my opinion he will be a black-red coder in the future.

    → Reply
»
3 months ago, # |
  Vote: I like it +12 Vote: I do not like it

They choose their IOI team really early. We only have our team after APIO, which is often in late May. China is just better.

→ Reply
»
2 months ago, # |
  Vote: I like it +45 Vote: I do not like it

The tasks have been published. You may upsolve the problems and view the specific scoreboard for each contest here.

→ Reply
»
2 months ago, # |
  Vote: I like it 0 Vote: I do not like it

Wondering where can one find the solution to previous CTT/CST problems?

→ Reply
»
2 months ago, # |
  Vote: I like it +9 Vote: I do not like it

How does it happen that people in the top 10 of CNOI tend to perform worse than people from top 20? If you got the first place at CNOI, it can't be just luck – but still the winner is now second to last.

→ Reply
  • »
    »
    2 months ago, # ^ |
      Vote: I like it +25 Vote: I do not like it

    It's just luck.

    → Reply
  • »
    »
    2 months ago, # ^ |
      Vote: I like it 0 Vote: I do not like it

    maybe this time the luck is not on his side, or maybe he has tried his best on his own this time, who knows?

    → Reply
  • »
    »
    2 months ago, # ^ |
      Vote: I like it +15 Vote: I do not like it

    I think this happens because the specific way problems are created and arranged for NOI and CTT is quite different. I don’t have solid proof, but here are a few key differences I’ve noticed:

    • Problem Order: In NOI, problems are always arranged in increasing difficulty, making it easier to pace yourself during the contest. On the other hand, CTT shuffles them randomly, which makes strategizing much harder.
    • Partial Scores:
    • NOI’s partial scoring system is pretty well thought out. It encourages you to move toward the full solution while still giving significant points for partial progress. You can often score quite a bit even if you don’t solve a problem completely.
    • CTT, however, seems to reward full solutions more and doesn’t benefit partial approaches as much. Some partial scoring setups even feel intentionally frustrating—like CTT24 D2T2, for example.
    • Interactive Problems: NOI typically has zero to one interactive problem, while CTT throws in several. This time, there were three interactive problems in total.

    Another thing to consider is that after NOI, a lot of Chinese participants start pre-university programs at THU or PKU, where they spend a lot of time on college-level courses. That takes away from their training time.

    → Reply
»
2 months ago, # |
← Rev. 2   Vote: I like it 0 Vote: I do not like it

I see some students are taking part unofficially, like Kevin or 郑煦翔. How can a student be an unofficial participant?

→ Reply
  • »
    »
    2 months ago, # ^ |
      Vote: I like it +3 Vote: I do not like it

    They are still in Junior High.

    → Reply
    • »
      »
      »
      2 months ago, # ^ |
        Vote: I like it 0 Vote: I do not like it

      Hmm, so anyone can be an unofficial participant? I thought they must meet some requirements.

      → Reply
»
4 weeks ago, # |
  Vote: I like it +43 Vote: I do not like it

The Final Contest of the China Team Selection has been ended.

Final Scoreboard: https://docs.google.com/spreadsheets/d/11Sh6zczubJ9eJxgSkyBcDL_EaZhHuwbyyZNlkLx1Avc

Note that according to the Chinese Rules, top 6 contestants will advance to the Interview & Thesis Defense round. The performance in the interviews will determine who will represent China in the IOI, (theoretically) regardless of any selection results.

→ Reply
  • »
    »
    4 weeks ago, # ^ |
      Vote: I like it +5 Vote: I do not like it

    What does the "bonus" score mean?

    → Reply
  • »
    »
    4 weeks ago, # ^ |
      Vote: I like it +5 Vote: I do not like it

    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?

    → Reply
    • »
      »
      »
      4 weeks ago, # ^ |
      ← Rev. 2   Vote: I like it +18 Vote: I do not like it

      Theoretically, yes. The official rule states that the top 6 will advance to the interview, and the team will be selected based on the interview performance only.

      However, #6 has never been selected for the national team. Most years, {#1, #2, #3, #4} end up in the national team, and sometimes #4 is replaced by #5.

      → Reply
  • »
    »
    4 weeks ago, # ^ |
      Vote: I like it +132 Vote: I do not like it

    I tried my best but Day2 is too hard for me… Choked on P1 then lost my way without the live standings. Solving 3 problems at a time was so exhausting! I’m a little disappointed that there isn’t any non-trivial data structure problems but lots of optimization and interactive problems.

    But the memories in these days are still unforgettable and impressive. I would not call myself the biggest loser because I enjoyed the whole session and liuhengxi, crazy_sea, JoesSR and umbrella-leaf are well deserved for their stable strong performances so it’s been a pleasure to compete with them.

    Technically my chance of being selected is below 0.01% since the scoring gap is quite large now, but I will perform my best in tomorrow’s thesis defense. Then I am going to explore the world of ICPC in next year. Thank everyone supporting me in this season!!

    → Reply
    • »
      »
      »
      4 weeks ago, # ^ |
        Vote: I like it 0 Vote: I do not like it

      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.)

      → Reply
»
4 weeks ago, # |
  Vote: I like it 0 Vote: I do not like it

I heard as part of selection students are qsked to prepare presentation. Is that not the case any more?

→ Reply
  • »
    »
    4 weeks ago, # ^ |
      Vote: I like it 0 Vote: I do not like it

    The tradition remains. The presentation is being done just these few days.

    → Reply
    • »
      »
      »
      4 weeks ago, # ^ |
        Vote: I like it 0 Vote: I do not like it

      I see. Any link that contains link to all the presentations from the recent years?

      → Reply
      • »
        »
        »
        »
        4 weeks ago, # ^ |
          Vote: I like it 0 Vote: I do not like it

        There's a github project which stores the paper,but I can find it right now.

        → Reply
  • »
    »
    4 weeks ago, # ^ |
      Vote: I like it +10 Vote: I do not like it

    That's a part of the "bonus score". And top 6 are required to make their presentation as a part of their interview to get selected as national team.

    → Reply
»
4 weeks ago, # |
  Vote: I like it +2 Vote: I do not like it

I wonder how do you get access to docs.google.com in China? Do you use VPN?

→ Reply
»
4 weeks ago, # |
  Vote: I like it +24 Vote: I do not like it

The tasks of the final stage can be found here: day1, day2. Problems are in Chinese only, and we might add a brief English translation a bit later.

→ Reply