The math and the overflow problem in problem D, also the geometry in problem E cooked me so bad. Not really enjoying this round.

Real fun playing, solving with the problems. Rank 12 overall, we are Addicted Tribes. Really, really looking forward to competing in the finals in Serbia :)

Also, we use GPT 5.4 Thinking, with some adjustments and refinements of strategies and ideas in the prompt to what we think would win past ideas. Some of the codes we ran for nearly an hour (bruteforcing) just to get the output file. I've never had a contest that was fun like this contest before.

First, I bet you'll see a test case with missing n quickly. Of course maybe some contest with ICPC format has it, but I don't think it's regular.

Second, why use the !(cin >> n)? If you are reading multiple strings or numbers, use while(cin >> n). If you are reading multiple lines, use while(getline(cin, s)). Checking the input in competitive programming is useless, ridiculous, and makes you look like AI (if not it is AI for real).

I don't think the !(cin >> n) is genuine. Please be honest. You are doing competitive programming, why do you have to check whether the input exists?

Well this is the mail I used to contact the Huawei team in both challenges in December 2025: challenge@huawei.com

They said that if you need to check or ask anything, just sent them a mail. If you can't reply to their mail in time, they will send you back a mail to claim the prize in early April due to changes in currency rate.

It's okay, they will send you back a letter to correct your info. If you can't reply in time, they will get in touch with you back in early April. No problem!

Well, congrats, it paid off :)

I don't think the code is $$$O(n^3)$$$.

I'm assuming that you are thinking the code has a cubic complexity in these line of codes:

    for (auto i : ord) {
        vector<char> forbid(n);
        int cc = 1;
        for (auto j : ord) {
            if (i == j || forbid[j] || a[j][i] == '0') continue;
            cc += indeg[j];
            for (int k : ing[j]) {
                forbid[k] = true;
            }
            ans.emplace_back(j, i);
        }
        debug(cc, indeg[i], ans);
        if (cc != indeg[i]) {
            cout << "No\n";
            return;
        }
    }

In the code, we have $$$cc = 1$$$ and $$$cc = cc + indeg[j]$$$ for each loop $$$i$$$. Due to that, after each $$$i$$$ runs successfully, we have $$$indeg[i] = 1 + indeg[j]$$$ for every $$$j$$$ that was chosen by the order. We also have the number of elements in $$$ing[j]$$$ equal to $$$indeg[j]$$$. Since $$$indeg[i] \le n - 1$$$, that makes the complexity of each loop $$$i$$$ linear. To sum up, the complexity is just $$$O(n^2)$$$.

Auto comment: topic has been updated by benben181 (previous revision, new revision, compare).

PLEASE DO NOT SUBMIT ANY CODE!

(VN) Tình huống khẩn cấp từ trang Codeforces. Đề nghị các thí sinh không nộp bài cuộc thi cho đến khi có thông báo mới. Có khả năng, đã có cuộc tấn công mạng nhắm vào trang Codeforces. Để đảm bảo an toàn thông tin, đề nghị các thí sinh hoãn nộp bài đến khi có thông báo mới. Trân trọng.

(EN) Emergency! Please do not submit your code in this contest until there is any other notifications from the Organizing Committee. It is likely that Codeforces is under a security attack. For safety in protecting personal information, please do not submit any of your code. Sincerely.

We expect to host it in 5 days straight. We apologize for any inconvenience, and we'll publish the announcement earlier in next seasons. We hope that you'll have a pleasant experience when participating in the contest, hope the problems will entertain you!

P/s: Note that the time solved in each problem is not a factor to calculate ranks, only the score and the number of submissions matter!

Right now, it is showing system testing for hours. This solution is stuck in getting the verdict "Running on test 2". Anyone have the same issue or is it just me?

Update: It has been fixed now.

If m = 0, then all elves must die. The only way we can't make all elves die is that the total amount of HP in all but the largest HP-value elf is strictly smaller than the largest HP-value elf. This is because we can always use the smaller-HP elves to attack the largest HP-value elf, therefore if after all the attacks the HP of the largest one is still larger than 0 then we can't do it.

Otherwise, we can attack the largest-HP elve by using the smallest-HP elf. At some point the largest-HP elve at the beginning will become the smallest-HP elve in the remaining elves (when using the "smallest" one to attack the "largest" one will result in a HP value of less than 0). When we reach this point, it is always possible to take (the initial value) of the smallest-HP one and the second smallest-HP one. The smaller one will die, and at the end of the process, both the two remaining ones will have HP < 0.

I have the same question. Will final testing rejudges all submissions or only the highest one?

Update: I got the response from the jury. Here it is.

From this announcement, we'll be able to send our solutions in about 2 hours from now.

Well, with the first test case both 2 3 or 3 2 are correct so I think there's no issue with the sample test case and explanation. Hope you had a great experience :)

About 3 weeks ago, yes. After that every contest that I tried to open submissions in standings and in status, all of them including my own was blocked. That is strange, maybe a bug in Codeforces? Anyway, I only hope that this issue will be fixed soon. There are already many technical issues on the page that need to be handled first.

Yes I hope so, because sometimes I also want to learn from other peoples' submissions as well (and also sometimes hack solutions). I've encountered this issue for over a week but there's still no support. I wanted to tag admins but I don't know if doing that may disrupts them.

How am I able to submit a hack if I can't view the code, when every submissions that I clicked in (even my own) display as "N/A"? Does anyone have the same issue like me? Please help me with this issue, I have had this issue for the last two weeks.

Does anyone have the same problem like me? I can see all submissions before Codeforces Global Round 30, but in a few recent rounds, I am not allowed to view any submissions. Even I can't view my own submissions. Is this a bug or a feature?

The contest was originally now, but was postponed due to Cloudflare's incident I think.