It is here: https://evaluator.hsin.hr/events/ -- is this what you are asking?

We were going to add a "COCI season icpc-style contest" to the gym sometime. I think oj.uz has separate contests usually.

Yeah, I take responsibility for the lack of storytelling in this round. But I think the story for Patkice compensates for Vepar and Hop.

The second problem on COCI is usually intended as an educational one in the Croatian version of the contest, so we may keep the stories shorter there.

It's centroid decomposition. In each subtree count number of pair $$$(v, u)$$$ such that $$$max(high(v), high(u)) - k\ge depth(v) + depth(u)$$$, where $$$high(v)$$$ is the maximum edge from root to $$$v$$$ and $$$depth(v)$$$ is the depth of $$$v$$$. This can be calculated using fenwick tree only.

Let $$$B_i = \lfloor \log_2 A_i \rfloor$$$. If there is an edge between $$$x, y$$$, then $$$B_x \lt B_y$$$. And $$$0 \le B_i \le 59$$$.

Now take a length-3 base-4 representation of $$$B_i$$$. For all $$$i, j$$$, print the first position where two length-3 numbers differ.

mkisic's implementation with Dijkstra runs in 1s (out of 2s TL), but the intended solution is the asymptotically faster 0-1 BFS, if I'm not mistaken.

The grouping of the tests into clusters is what IOI does, and COCI is primarly intended as a training contest for Croatian high school competitors. Although, I guess we could work on making clusters more granular.

Digression: we encourage feedback like this, all contestants (both on COCI and the Croatian version) who have feedback on the problems, the best place is these Codeforces threads for COCI.

There were only 4 million vertices though, right? What I did, and I assume it's the intended solution, was 0-1 BFS which probably makes a significant difference.

Sorry, I should have elaborated a bit more, but writing is hard...

The notation $$$v_p(x)$$$ denotes the "largest power of $$$p$$$ that divides $$$x$$$". For example, $$$v_2(8) = 3, v_5(100) = 2, v_3(7) = 0$$$. You may have seen the Fundamental Theorem of Arithmetic in this form: $$$n = \prod_{p} p^{v_p(n)}.$$$

This $$$v_p$$$ comes up in problems that ask for divisibility, because if $$$y$$$ is a multiple of $$$x$$$, then $$$v_p(y) \ge v_p(x)$$$.

In this task, we use https://en.wikipedia.org/wiki/Legendre%27s_formula to calculate $$$v_p$$$ of an interval -- although you could probably come up with the formula by yourself, the proof is a single line.

Can anyone well versed in Codeforces problems give an example where a similar approach is used?

go to this website Tasks-> HONI-> 2020./2021. -> 4.kolo

Something’s wrong with your checker — my solution got 0 points on your judging system but got full points on hsin.hr. here is my solution: https://oj.uz/submission/1281070