Hello everyone,

Upd: Livestream has been scheduled. Time in your timezone. You can tune in here. Upd2: We recorded it with live audience today. Audio was lagging at some places. I will edit it by next week and upload it.

I wanted to share some exciting news with you. Recently, I launched my YouTube channel and created a community Discord server. Up until now, I've mainly focused on hosting post-contest discussion streams on my channel. However, I have plans to diversify the content.

To kick things off, I'm thrilled to announce that I've invited my arch-rival, and my best friend, TheOneYouWant, to join me for an Ask Me Anything (AMA) session on my channel. We are planning to record this AMA sometime next month.

Shubham (aka TheOneYouWant) is one of my best friends I've met through CP. He started CP after taking a programming class at IITB, and soon became obsessed — he ended up qualifying for WF thrice! After graduating from IITB, he went to grad school at Stanford, and now works as a software developer at a quant firm in New York. He's enjoyed teaching through his years; he used to teach for math olympiads through undergrad, and was head TA for algorithms in grad school. In his free time, Shubham likes to read manga, play badminton, and write blogs. Often, he's thinking about the next random thing to get obsessed with...

Feel free to ask anything you're curious about, although he can't guarantee he'll answer every question. If you're interested in following TheOneYouWant on his journey/reading more about his thoughts, consider following him on Twitter here and his blog here.

Hi Codeforces,

ICPC Kanpur 2023 Regionals Round will happen this Saturday on CodeDrills.

Live commentary: We will be live on codedrills youtube channel. We will start once the contest starts.

• Contest Link — https://icpc.codedrills.io/contests/icpc-kanpur-2023-regional-round
• Ranklist — https://icpc.codedrills.io/contests/icpc-kanpur-2023-regional-round/scoreboard
• Date & Time — 23 Dec 2023, Saturday, 10:00 IST
• Duration — 5 Hours
• There will be 1 to 20 problems to solve
• Will follow standard ICPC scoring system (20 minutes penalty and 1 point per problem)
• The questions may not be sorted by difficulty

P.S. — All of the problems will be non-interactive, please read the guide of interactive problems before the contest.
P.P.S. — Some problems may have subtasks, so choose problem-solving order wisely.

#pragma GCC target ("sse4")
#include <bits/stdc++.h>

int main(void) {
    std::set<int> s;
    return 0;
}

It fails to compile with error
In file included from /usr/include/c++/13.1.1/string:43, from /usr/include/c++/13.1.1/bitset:52, from /usr/include/c++/13.1.1/x86_64-pc-linux-gnu/bits/stdc++.h:52, from a.cpp:2: /usr/include/c++/13.1.1/bits/allocator.h: In destructor ‘std::_Rb_tree<int, int, std::_Identity<int>, std::less<int>, std::allocator<int> >::_Rb_tree_impl<std::less<int>, true>::~_Rb_tree_impl()’: /usr/include/c++/13.1.1/bits/allocator.h:184:7: error: inlining failed in call to ‘always_inline’ ‘std::allocator< <template-parameter-1-1> >::~allocator() noexcept [with _Tp = std::_Rb_tree_node<int>]’: target specific option mismatch 184 | ~allocator() _GLIBCXX_NOTHROW { } | ^ In file included from /usr/include/c++/13.1.1/map:62, from /usr/include/c++/13.1.1/x86_64-pc-linux-gnu/bits/stdc++.h:152: /usr/include/c++/13.1.1/bits/stl_tree.h:662:16: note: called from here 662 | struct _Rb_tree_impl

Compilation command — time g++ -static -DONLINE_JUDGE -O2 -std=c++20 $$${file} -o $$${file}.exe

G++/GCC version g++ (GCC) 13.1.1 20230429 Copyright (C) 2023 Free Software Foundation, Inc. This is free software; see the source for copying conditions. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

When, where and how to report it?

Update: GCC Bugzilla

Hi Codeforces,

ICPC Asia West Continent Final Contest 2022 will happen ~10 hrs from now on CodeDrills.

Live commentary: We will be live on codedrills youtube channel. We will start once contest starts.

Contest Details

• Contest Link — ICPC Asia West Continent Final Contest 2022
• Date & Time — 20 May 2023, Saturday, 11:00 IST
• Duration — 5 Hours
• There will be 8 to 20 problems to solve
• Will follow standard ICPC scoring system (20 minutes penalty and 1 point per problem)
• The questions may not be sorted by difficulty

P.S. — All of the problems will be non-interactive, please read the guide of interactive problems before the contest.
P.P.S. — Some problems may have subtasks, so choose problem-solving order wisely.

Update: Live ranklist
We plan to start live commentary 1 hr into the contest. Commentry URL

Update 2 — Credits
Chief Judge: Jatin jtnydv25 Yadav
Setters: Jatin jtnydv25 Yadav, Nishank IceKnight1093 Suresh, Jeroen Op de jeroenodb Beek, Vsevolod sevlll777 Lepeshov, Arul flamestorm Kolla
Testers (excluding setters): Aryan aryanc403 Choudhary, Chaithanya Dragonado Shyam, Vaibhav xennygrimmato Tulsyan, Ritul Kumar ritul_kr_singh Singh, Kshitij kshitij_sodani Sodani, Praveen PraveenDhinwa Dhinwa, Siddhartha gravito12345 Srivastava, Konstantin miagkov Miagkov
Codedrills platform: Deepa deepa_panwar Panwar, Balajiganapathi Balajiganapathi S, Swati Panwar, Vichitr Vichitr Gandas
Rcd: Prof. Phalguni Gupta

Results
Final ranklist
1. facelessmen3.0 (IIT Kanpur) — satyam343 udhavvarma03 avi0000
2. Ab_Ki_Baar (IIT Kharagpur) — professor_flux harsh639 RahulChugh
3. Yorozuya Forever (IIT Madras) — Teja-Smart blitztage Nisanth

We will try to hold one universal cup stage based on Amritapuri (Regionals+Online), and Asia West Finals problems.

Hi Codeforces,

ICPC Amritapuri 2022 Regionals Round is happening right now on Codedrills.

Live ranklist: https://icpc.codedrills.io/contests/icpc-amritapuri-2022-regional-round/scoreboard

Live commentary: We will be live on codedrills youtube channel. We will be starting soon.
Update: We are live now.

Contest Details
- Contest Link — ICPC Amritapuri 2022 Regionals Round
- Date & Time — 2 April 2023, Sunday, 9:00 IST
- Duration — 5 Hours
- There will be 12 problems to solve
- Will follow standard ICPC scoring system (20 minutes penalty and 1 point per problem)
- The questions may not be sorted by difficulty
- Contest link — https://icpc.codedrills.io/contests/icpc-amritapuri-2022-regional-round

Edit — Credits
Chief Judge: Jatin jtnydv25 Yadav
Setters: Janmansh janmansh Agarwal, Aryan aryanc403 Choudhary, Jatin jtnydv25 Yadav, Chaithanya Dragonado Shyam, Vaibhav xennygrimmato Tulsyan, Mukesh Kumar, Jatin rivalq Garg, Vaibhav gvaibhav21 Gosain, Harris gamegame Leung
Testers (excluding setters): Aswin aswinashok44 Ashok, Mayank katana_handler Pugalia, Nishank IceKnight1093 Suresh, Ritul Kumar ritul_kr_singh Singh, Kshitij kshitij_sodani Sodani, Abhay Pratap abhayps Singh, Mohan Raghu mohanraghug Garimella, Ankur ankurkayal Kayal, Praveen PraveenDhinwa Dhinwa, Sai sinus_070 Avinash, Siddhartha gravito12345 Srivastava, Osama ......-......... Saleh, Anil marksman_ Kumar, Masood Alam
Platform Coordinators: Deepa deepa_panwar Panwar, Balajiganapathi Balajiganapathi S, Swati Panwar, Vichitr Vichitr Gandas
RCD: Maheshwara anandoham Chaitanya

Edit 2: Results
1. Paradigm Shift (IIT Indore) — codebuster_10 s_jaskaran_s nishkarsh
2. AuditPass (IIT Delhi) — tamajitbuba islingr magga
3. :(){ :|:& };: (BITS Pilani, Hyderabad Campus) — ExplodingFreeze JeevanJyot the_hyp0cr1t3
4. Maanzar (IIT Patna) — 100gods AwakeAnay TimeWarp101

Hi everyone,

We are looking for problem-setters to join the ICPC Asia West Finals 2022-23 panel and contribute interesting tasks. If you or anyone you know is interested, please fill this form. You are also welcome to join the team to help in testing, task preparation etc.

Eligibility:

• For Indians, you should have graduated in 2021 or before. School students, no longer eligible for ICPC (due to age limit, exhaust WFs/regionals attempts etc) and ICPC WF Egypt I qualified participants (if they are not participating again) can also contribute problems.
• Preferably, should have a track record of participation in similar contests or good profiles on online competition platforms like Codeforces, AtCoder, CodeChef, etc.
• For non-Indians, anyone not participating in Indian, Asia West Regionals.

Compensation

Problem setters would be paid with the following per-problem rates (difficulty determined by the contest admin)

• Cakewalk: 1500 INR
• Simple: 2250 INR
• Easy: 3750 INR
• Easy-Medium: 6000 INR
• Medium: 9500 INR
• Medium-Hard: 13000 INR
• Hard: 19000 INR

For preparation, setting amount is split half-half between author and preparer.

Update: I removed tester compensation because I'm unsure how it will be distributed among multiple testers.
Update2: The judge does not have support for interactive problems, so we won't be able to accept those proposals either.

Update 2 — Thanks adamant for his Subset convolution interpretation blog. It does simplifies a lot of things.

Update 1 -
Let's consider this problem -
We have a function subset_convolution(A,B) it gives us Subset Sum Convolution of two sets $$$A, B$$$.
Let's say we array $$$A$$$ with $$$A[0]=1$$$ and we want to find A^K defined as $$$A$$$ convoluted with itself $$$K$$$ times.
A^2 = subset_convolution(A,A)
A^3 = subset_convolution(A^2,A)
...
A^k = subset_convolution(A^{k-1},A)
The best I can think right now is using something on lines of fast exponential to achieve $$$O(log K*N^2*2^N)$$$ time where $$$2^N$$$ is the size of A. Also, there exist some solutions $$$O(N^3*2^N)$$$ using the fact that the majority of the multiplications will be with A[0] and permutations & combinations.
But it can be done in $$$O(N^2*2^N)$$$ using tricks well known at some places. Idk why it works tho.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

TLDR — Just me rambling about the old ARC problem I was solving for the last 3 days. Something "set power series" similar to "power series for polynomials" I came across and I have an iota idea about it right now. Also amplifying some unanswered bugaboo related to it in the discussion of that ARC round. Spoiler is just very very briefly mention different solutions I had for ARC105F problem.

The logarithm of 'set power series' is a function $$$g(x)=\sum_{S} g_{S} x^{S}$$$ such that $$$f(x) = \sum_{S} (\sum_{\mathcal{P}} \prod_{P_i \in \mathcal{P}} g_{P_i}) x^{S}$$$, where the inner summation goes over all unordered partitions $$$P$$$ of $$$S$$$.

dario2994 submission on the same problem implements a small library for subsets with functions namely and/or/xor/subset convolutions along with log and exp of set power series.
(First to answer dario2994 comment — Yes, there does exist a clever way (and maroonrk's submission) to compute subset convolution.)

I did asked some of my friends and seniors doing MATH major — where can I read formal definitions of "set power series" since googling it just gave me useless results and none of them ever heard it.

Q1 — What exactly is the definition of exp of set power series? (One implemented by dario2994 and mentioned by mmaxio). Where can I read about more similar definitions?

mmaxio mentions Lu Kaifeng's report, googling about his report along with keywords such as "set power series" doesn't yield helpful results. But then I came across this blog. It has a code snippet and mentions For details, please refer to the 2015 Proceedings of the National Training Team Lu Kaifeng, "The Properties and Application of Set Power Series and Its Fast Algorithm".

It's a 17 page report published in 2015 in Chinese, I wasn't able to find an English version. Hence must be a well-known problem in China and hence a "trivial solution" by Elegia. I tried auto translating it using the method mentioned by z4120 in Auto-translated Chinese national IOI training team report papers but I messed up a step somewhere and ended up with just Chinese translated into Chinese, would really appreciate it if someone can translate it for me.

Q2 — mmaxio's comment looks like you can apply any function to the set power series by applying it to a "ranked" vector for each mask independently makes me much more interested in this. It opens the door to a hell of a lot of possibilities here (a reason for this blog here) integration, derivative, inverse, square root to name some among similar operations on polynomials and series.

I do remember the day when I learnt about the inverse and square root of a polynomial and was overwhelmed by it. On that day, I just concluded that "polynomials are just numbers". Later I have seen some problems which even used dp states as polynomials instead of integers. The observation "polynomials are just numbers" makes it easy for me to understand those editorials and those problems do excite me these days. Something similar for sets will for sure generalize it further.

Publishing this blog with the expectation that I would find more material to read about it since Google isn't my friend here.

Update 1 (solution) —

Notification, when someone in your friend list writes a comment or creates a blog, is too annoying. Can someone make it opt-in?
/cc geranazavr555 MikeMirzayanov

Update 1: Apologies to 1595 people who got pinged due to this blog.
Update 2: I just realised codechef advertised their upcoming contest to 9298 people without spending a single penny. GG.

Part 0
Part 1a Part 1b Part 1c

17 Dec 2019 -

3 March 2020 -

Finally on 16 Nov 2020 -

And the hunt continues.

The 20th round of the first vintage Universal Cup is happening the weekend of June 17th. The contest is based on the Asia West Championship and Asia Amritapuri (Regionals+Online) problems.

As always, there are three time windows for you to join:

• June 17th 13:00 — 18:00 (UTC +8)
• June 17th 19:00 — 24:00 (UTC +8)
• June 18th 02:00 — 07:00 (UTC +8)

Please note that you can see two scoreboards in DOMjudge. The 'Local Scoreboard' shows the standings ONLY IN THE CURRENT TIME WINDOW. And the 'Combined Scoreboard' shows all participants, including the onsite participants, and the cup participants in the previous time windows.

Contest link: https://domjudge.qoj.ac/

Universal Cup Scoreboard: https://qoj.ac/ucup/scoreboard

About Universal Cup:

Universal Cup is a non-profit organization dedicated to providing trainings for competitive programming teams. Up to now, there are more than 600 teams from all over the world registering for Universal Cup.

A more detailed introduction: https://codeforces.net/blog/entry/111672

Register a new team: https://ucup.ac/register (the registration request will be processed before each stage)

Results of the past stages: https://ucup.ac/results

Terms: https://ucup.ac/terms

Ratings: https://ucup.ac/rating

hmehta didnt made an announcement on CF :/
SRM 756 will be held today.(in less than 30 mins) Atleast topcoder site says so.

Time: 16:30 UTC+5:30, April 25, 2019

Lets discuss problems after the contest.

MikeMirzayanov
Can you please add an unofficial checkbox on a user profiles contest page (e.g. — My Profile's Contest Page) similar to the submissions page.
Unofficial contests can include Unrated, out of competition contests. And maybe virtual participation as well.
Thank you.

We are trying to add our first gym contest for members of our college in our CF group.
We have added problems on polygon platform.

For adding problem in group We came across https://codeforces.net/blog/entry/10077?locale=en . We have followed preliminaries of Polygon and up to step 2 of CF.

For the third step, we need one directory at ftp://taskbook.codeforces.com . Unfortunately, it is showing the following error.

→ External storage error
The external storage was offline or malfunctioned during the last contest update. Please wait for some time, then go to the contest edit page and click "Save changes" to synchronize data

MikeMirzayanov please fix this issue asap. So that we can add problems for our group. We are planning to start the contest by Thursday evening. And we have less than 24 hrs.

We express gratitude to MikeMirzayanov and the rest of the team for the great Codeforces and the wonderful Polygon platform.

Upd: Issue was fixed within 15 minutes after this blog.
Maybe It was due to this blog or they were already working on it.

Since ICPC season is underway. In past, Three Codeforces Trainings Seasons (in 2013-14, 14-15, 16-17) and one on codechef) were organized.
Can someone organize one for this season also?