Hi everyone,
I am happy to announce that the 2019 Southeastern Europe Regional Contest will take place on October 19 in Bucharest and Vinnytsia at 10 am UTC+3. The link to the live results will be published here after the start of the competition.
Moreover, in the following day, there will be the Grand Prix of Southeastern Europe based on these problems at 8 am UTC. If you do not participate in it, you will be able to take part in online mirror, which will be available at the same time.
Because of the Grand Prix, we are asking the official contestants not to discuss the problems in public.
After it, we will upload the contest to the gym and publish the editorial.
Good luck!
UPD. SEERC standings.
UPD2. Congratulations to the winners!
| Place | Team Name | Contestant 1 | Contestant 2 | Contestant 3 | Problems | Penalty |
|---|---|---|---|---|---|---|
| 1 | [UNIBUC] ScrambledEggs | bicsi | theodor.moroianu | livlivi | 8 | 1001 |
| 2 | KhNURE_NRG | BigBag | Mustang98 | shanin | 8 | 1077 |
| 3 | RAF Penguins | Pajaraja | milisav | allllekssssa | 8 | 1401 |
| 4 | KhNU_DOROGA* | Stroustrup | kilt_01 | 13022001 | 7 | 976 |
| 5 | KNU_MaxFun | Adalbert | Barichek | Markellonchik | 7 | 1027 |
| 6 | UNAGI | osmanorhan | ikbal | ozcelik | 7 | 1498 |
| 7 | LNU Jackals | Danylo99 | mshcherba | BohdanPastuschak | 6 | 508 |
| 8 | UBB_HakunaMatata | Bodo | sebinechita | Cozma_Tudor | 6 | 719 |
| 9 | KNU_Kektus* | danya.smelskiy | iSlava | PashaChemerys | 6 | 777 |
| 10 | [UAIC] VYE | Juve45 | cristian1997 | denis2111 | 6 | 824 |
UPD3. Online mirror will be available here. PS. You should join the group first. The mirror will start after the Open Cup.
UPD4. Editorial is here.
UPD5. The contest is available in the gym.
And this GP clashes with cf div 1, right?
That's true. However, we can't fix it.
In VYE team, the third correct person is cristian1997
Thank you! Fixed.
I am positively surprised by the quality of problems. I associated SEERCs with very bad problems, but they were actually quite good (except tedious K), I would say CFH were AtCoder quality problems
F was the only problem I didn't like because it's well known for general graphs.
Ok, yeah, maybe you're right. It is kind of prerequisite to know this, so maybe it is not that good problem, but I have always loved this fact for general graphs
Agree, it’s one of my favorite results but the problem will be sad in contest if you haven’t seen it before.
Can you provide the link for problem in general case?
or aid maybe
https://core.ac.uk/download/pdf/82376548.pdf section 1 has it
And a good quality editorial, as well.
How many teams qualified to WF from SEERC ?
3-6 teams, I guess. But that will be known much later.
There is another way to come to solution for problem F.
Let's count the number of times first player can win in subtree, assuming black vertices remain black -- $$$f(v)$$$. Each player can refuse to move and lose.
If all sons are losing than first player chooses the root and second player then refuses to move. So in such case $$$f(v)=1$$$.
If there are at least 1 winning son, first player wins in that son forcing second player to move the root and then first player moves again to the same or another winning son. All other times second player can't move to the root, so first player just wins all sons, so $$$f(v)=\sum{f(to)} - 1$$$