We will hold AtCoder Regular Contest 212 (Div. 2).
- Contest URL: https://atcoder.jp/contests/arc212
- Start Time: http://www.timeanddate.com/worldclock/fixedtime.html?iso=20260111T2100&p1=248
- Duration: 120 minutes
- Number of Tasks: 6
- Writer: milkcoffee
- Tester: Nyaan, maspy
- Rated range: 1200 ~ 2399
The point values will be 400-500-600-600-700-700.
We are looking forward to your participation!
Why 6 problems this time?
I think there is an approach for C using a Gf, which seems more natural and intuitive.
Edit: shobonvip has just written an editorial about this.
I OEIS'd. It gives you the function
1/((1-x)(1-x^2))^K.ARC problem be like:
When I opened the problem statement, memories suddenly flooded back. It was exactly the same feeling I had a few months ago when I opened the problem statement for the China NOI2025. In short, it was all about "modulo something".
The final result was almost identical. The loss in ARC212 made me a bit frustrated, and the NOI loss almost negated all my efforts over the past year.
hill climbing for a icpc-type problem ???
There is a determined solution for problem D.
I can't understand one thing in editorial of problem A. We assume that cycle must contain 4 edges. But what if we had graph where (1, 2) = 1; (1, 3) = 1 (1, 4) = 1 and other edges equals to 1000. Then we have cycle 1->2->1->3->1->4->1 that passes through all vertices, but not only once.
Sir this is not a cycle...
I'm an idiot... Edges can't repeat in a cycle. Why I even thought otherwise? It happens sometimes I guess...
Can anybody prove "the higher the score, the more people are in a good state." in D's editorial. I can't understand this observation.
The statement is false. But intuitively a high score somehow correlates with a high number of people in a good state. I think the statement is only trying to give an intuitive reason, why we use that score to prove that the process of "putting people that are in a bad state into the other room, until no more such people exist" terminates in finite time.
OK. after thinking I proved it (not the observation but the algorithm). This is a hill climbing. We can move in the hilly area by flipping a person. If this flipping turns a person to good, $$$f$$$ will increase, else, $$$f$$$ will decrease. So all hilltops (whom if we flip any person will make $$$f$$$ decrease) is a state that everyone is good. The $$$f$$$ is at most $$$n^2\times V\le 250000$$$, in each step we will increase $$$f$$$, so we can reach a hilltop in $$$250000$$$ times of flipping.
I gave https://atcoder.jp/contests/arc212 today. After sometime I checked my profile is not found and I am unable to login. There is no mail communication from Atcoder team. When clicked forgot username and entered mail id to recover username it shows some else username instead my atcoder username was timeisvaccum and my contest history is deleted of last 6 months. Did anyone experience the same what does it mean? There is only one mail id linked to atcoder and only one username.
PS: Issue is fixed now. It was login issue at Atcoder's end.