The European Championship 2025 will take place on the 2nd of March in Porto. The top teams from the European ICPC regionals CERC, NWERC, SEERC, SWERC will compete for the title of European champions. It is the second edition of this ICPC super-regional.
The mirror contest European Championship 2025 - Online Mirror (Unrated, ICPC Rules, Teams Preferred) will be held on Codeforces at Mar/02/2025 13:35 (Moscow time) and will last 5 hours.
The mirror contest will feature the same problems as the official competition, except for one problem, which will be presented in a more challenging version.
I am the chief judge for the competition and I want to thank:
- The amazing set of judges who proposed and prepared the problems: bicsi, cip999, cdkrot, Egor, gangsterveggies, Giove, Jorke, Petr, thocevar.
- Our beloved tester ksun48.
- Everyone involved in the organization of EUC, in particular our director Fernando Silva.
- The developers of DOMjudge, the contest system used in the official contest.
- MikeMirzayanov for Polygon (that we used to prepare the problems) and for letting us host the mirror on Codeforces.
I invite you to participate in the contest and I hope that you will like the problems.
On the difficulty
The contest features problems with difficulties from div1A to div1E. It should be enjoyable for many, and interesting even for the strongest teams in the world.
Rules
- The contest is unrated, so your codeforces rating will not be affected.
- The scoring is ICPC-style: teams are first sorted by number of problems solved, then the time-penalty is used as a tie-break. An incorrect submission gives a 20 minutes penalty.
- We encourage participation as a team.
- If you are participating in a team, we encourage you to use only one computer for coding the solutions (as in an ICPC contest). Regarding using templates, googling, and copy-pasting code: feel free to do it.
UPDATE 1: Here you can find the editorial: https://codeforces.me/blog/entry/140239
UPDATE 2:
Congratulations to the winners, and especially to the first team for AK:
I almost had a heart attack when I read this: "will take place on the 2nd of March in Prague"
When I heard about the European Championship 2025, I knew this was my chance to showcase my skills… or to witness my own failure in real time.
Battle Plan:
Start with the easiest problem to build confidence. Realize that even the easiest problem requires logic I clearly don’t have. Move on to the next problem, hoping for divine inspiration. End up opening a text editor just to write return 42;. The ICPC format encourages teamwork. Unfortunately, my main teammate is myself and my tendency to overthink simple problems. But no worries, I read somewhere that staring at a problem statement for five hours is an underrated problem-solving technique.
If I finish in the top 10, I’ll write a tutorial on “How to Solve Problems by Staring at Your Screen.” If I solve nothing, I’ll blame a mysterious system error beyond my control.
Either way, it’ll be an intellectual adventure. And if things go south, at least I can say I was there.
I admire your strategy—staring at the problem long enough until it either solves itself or I start questioning my life choices is also my go-to approach.
Teamwork sounds great, but let’s be honest: the real struggle is negotiating with my own brain to function under pressure. If I get a single problem right, I’m declaring victory and writing a motivational book titled "Debugging My Soul: A Journey Through ICPC."
But in the end, whether I solve problems or just contemplate their philosophical depth, at least I’ll have five hours of quality time with my keyboard.
This reminds of Obama meme for a reason XD
I am looking forward to it.
Problems are nice to stare at, not to solve.
My Skill Issue ;-;
I don't enjoy your judged problems; they don't feel exciting to me.
It seems like you are trying to make thinking-oriented ad-hoc problems (similar to Atcoder or NEERC regional ones). But it looks unnatural, like forced in some way so that problems become more ad-hoc.
It's not like I don't enjoy such problems (they're one of my favorites), but I don't know. The joy of such problems is that they are natural, that you get an AHA moment. From your problems, I don't feel it.
Thank you for sharing your feedback. Though, honestly, I cannot really understand what you are trying to express. But I understand that you did not enjoy the contest and I hope that next time you'll enjoy more our contests.
non-constructive version of feedback: there are too many boring adhoc problems.
I have a probabilistic solution for Problem A (optimised) https://codeforces.me/contest/2068/submission/308681793
The probabilistic solution we could come up with (more precisely, the tester came up with) does not work well enough. Congrats on getting AC in this way.
We could have avoided it by asking $$$k\le n$$$ but that would have made the problem harder. Moreover, I think that probabilistic solutions are fun.
ya the initial one i got tons of wrong answers as well, had to do random shuffle for the adjacency list of all the numbers as well and then half of the times put the array in the front and the other half of the times at the back of the permutation.
Ya probabilistic solutions are always fun.
We had a randomized solution from tester, which we even initially thought is a correct one — i.e. I wrote a proof that if number of voters used goes to infinity, the probability of that solution working converges to one. However with good test data for the constraints $$$n:=50$$$, $$$maxvoters=50k$$$, the probability of success is like $$$0.05$$$, and it takes that solution 5-10xTL time to find answer.
So I expected that if you come up with several creative hacks it might be good enough. Arguably it's more work than writing intended solution though:). Hope you had fun though, randomized algorithms are neat.
Ya it was real fun thinking of optimising the low probability of success solution.
Problems are nice.
Thank you!
Subset of array does not have to maintain order right? {3, 1} would still be subset of [1, 3, 4] isn't it? I think on problem J, it should be subsequence instead of subset. Otherwise solution would just be to check if there is even number of white wine in the first N wine. I could be completely wrong though, if so pls correct.