XX Open Cup Grand Prix of Gomel takes place on Sunday, February 16, 2020, at 11:00 AM Petrozavodsk time.
The links to the contest:
You need an Open Cup login to participate.
I'm the writer of all the problems. Let's discuss them here after the contest!
UPD: Thanks for your participation! Editorial is available.
When I login into the page I get the following message: "The virtual contest is in progress. You are not allowed to participate".
EDIT: Now both links given for Div 1. seem broken to me.
EDIT2: fixed, thanks :D
How to solve B and H?
How to solve E?
Let P(X)=∑pi⋅xi. We need to find several first coefficients of Q(x)=P(x)n.
We can write equation Q′(x)=(P(X)n)′=n⋅(P(x)n−1)P′(x)=n⋅Q(x)/P(x)∗P′(x)
So P(x)⋅Q′(x)=n⋅Q(x)⋅P′(x). If we write everything about xm it will give us a way to represent (m+1)-th of coefficient of Q(x) from deg(P) previous.
Only after reading editorial for A I noticed that it's guaranteed that n is divisible by k. :)
How can I obtain an opencup account? I've messaged snarknews on CF but got no response.
There is linear solution for F based on fact we can calculate f(k)=∑t≥nbin(k,t) for all k in linear time
Instead of matching algorithms for G we can use much much simpler approach (especially when compared to blossom): take arbitrary unmatched vertex and match it to its random neighbour — if it that random neighbour was already matched before then unmatch it
What about the bipartite part? This method works for it too?
Yeah, works like a charm for both bipartite and non-bipartite case :)
We can use the symmetric chain decomposition of the boolean lattice to solve the bipartite case for G constructively. You can read pages 5 and 6 of this slide.
orz jqdai0815 teacher
Comments like this make me realize that I haven't even started CP xD
Will the mirror of this contest available anytime soon on Codeforces gym?