$p = 1$ is easy, just check if the virus is completely safe in its, check if the virus is completely safe in its initial cell. Let's focus on $p =
2$. For a pair $(i, $ with virus $i$). Otherwise, if there are two attacks to the same cell, we can
ignore the first one, , maintain the position of the strongest safe virus. When a new safe virus
appears (because we moved to, For a pair $(i, j)$, we want to check if the virus $i$ can get to the cell $j$
and be safe there, Or you can use bitsets. For a virus in its initial cell, store a bitset of
viruses that can kill
→ Pay attention
→ Top rated
| # | User | Rating |
|---|---|---|
| 1 | Benq | 3676 |
| 2 | Kevin114514 | 3659 |
| 3 | jiangly | 3640 |
| 4 | turmax | 3450 |
| 5 | tourist | 3408 |
| 6 | strapple | 3360 |
| 7 | Um_nik | 3354 |
| 8 | squareOf105 | 3348 |
| 9 | maroonrk | 3312 |
| 10 | idontwannadothis…e | 3191 |
→ Top contributors
| # | User | Contrib. |
|---|---|---|
| 1 | Qingyu | 154 |
| 2 | nik_exists | 151 |
| 3 | maspy | 149 |
| 4 | AmShZ | 146 |
| 5 | Um_nik | 143 |
| 6 | Errichto | 139 |
| 7 | BledDest | 136 |
| 8 | adamant | 135 |
| 9 | maroonrk | 133 |
| 10 | cry | 130 |
→ Find user
→ Recent actions
You can use several words in query to find by all of them at the same time. In addition, if you are lucky search understands word forms and some synonyms. It supports search by title and author. Examples:
305— search for 305, most probably it will find blogs about the Round 305andrew stankevich contests— search for words "andrew", "stankevich" and "contests" at the same timeuser:mikemirzayanov title:testlib— search containing "testlib" in title by MikeMirzayanov"vk cup"— use quotes to find phrase as istitle:educational— search in title
Results
1.
ROI 2018 in GYM Hi.
On Wednesday at [9:05 CET / 8:05 UCT](https://www.timeanddate.com/worldclock/fixedtime.html?day=27&month=3&year=2019&hour=11&min=5&sec=0&p1=166) you can participate in the GYM version of the finals of 2017-2018 Russian Olympiad in Informatics (ROI), Day 1.
And on Thursday there will be day 2, same time.
Links to GYM contets: [day1](https://codeforces.me/gym/102147) and [day2](https://codeforces.me/gym/102154).
5 hours, 4 problems, IOI-style scoring with subtasks.
Statements will be available in three languages: English, Russian, Polish.
We wanted to use those problems in a camp in Warsaw so we had to import the problems to some system anyway.
Then why not Polygon+Codeforces and thus allowing everybody to participate?
Huge thanks to [user:MikeMirzayanov,2019-03-25] for helping me with using GYM.
And credits to problem authors: [user:Andreikkaa,2019-05-21] for Radium, [user:Endagorion,2019-05-21] for Viruses, [user:pashka,2019-05-21] for Innophone, Георгий Корнее...
2.
Some notes on rating inflation ### Introduction
Recently there have been several suggestions that there is significant rating inflation now due to COVID-19. The typical hypothesis seems to be along the lines of:
> Because people stay at home more now, there is a lot of new inexperienced users who add a lot of rating to the system, pushing "old" users upwards without actual improvement.
A simplified and a bit more general hypothesis that I'm going to test:
> Because of the virus I'm gaining more rating than usual without working more.
But most of these comments are based on anecdotal evidence, which is not worth much.
I wanted to see if there is any truth to these claims.
Specifically, this blog is an implementation (although I modified the approach a bit) of the following [comment](https://codeforces.me/blog/entry/20638?#comment-601634) by [user:geckods,2020-04-15]:
[cut]
$~$
### Methodology
Let's define the "test period" and "control period".
...
general hypothesis that I'm going to test: > Because of the virus I'm gaining
more rating than usual, > Because of the virus I'm gaining more rating than usual without working more.
3.
BOI 2021 The year is 2021. Like every year, contestants from all of the baltic countries meet for the Baltic Olympiad in Informatics. Well, not entirely... One small virus still holds the entire world under its spell. And life is not easy for BOI contestants who have to participate remotely from their own homes...
This weekend, the **Baltic Olympiad in Informatics 2021** (BOI 2021) is going to take place! BOI is a programming contest for secondary school students from countries around or close to the Baltic sea. This year, around 60 contestants from Denmark, Estonia, Finland, Germany, Latvia, Lithuania, Norway, Poland, Sweden and our guest countries Israel and Ukraine will compete against each other, solving difficult problems of algorithmic nature. Each participating country sends 6 contestants from their national olympiads which take place in the months beforehand.
The contest consists of two days, Saturday an...
Olympiad in Informatics. Well, not entirely... One small virus still holds the
entire world under
4.
Problems that I authored so far Hi everyone,
after [contest:1854], maybe it's time to collect all my problems here. For now, I've mainly invented easy-ish problems. I wish to invent a very hard problem sooner or later :)
<spoiler summary="Update after Pinely Round 3">
Done :D
</spoiler>
I'm putting the story of each problem under spoiler, because it may contain parts of the solution. I invented many problems by just trying random setups until I came up with something solvable, but some problems (especially the harder ones, for example [problem:1854D]) may have more interesting stories.
Fun facts:
- I struggled a lot to find a suitable div2A for [contest:1654]. I proposed a lot of problems that turned out to be unsuitable (for example, because they were too hard), then I used them somewhere else.
- While I was writing this blog, I realized that [problem:1849E] is identical to my problem [preoii_allenamento \- Allenamento su ChinaForces](https://training.olinfo.it/#/task/preoii_allenamento/statement),...
. First, I overkilled [problem:1787D], using the random solution from [JOI 2019
—Virus, First, I overkilled [problem:1787D], using the random solution from [JOI 2019 —
Virus
5.
AtCoder WTF 2020 will be postponed because of Corona Virus Unfortunately, due to the new Corona Virus problem, we decided to postpone WTF 2020.
In Japan, various sport events were cancelled recently (for example football matches). We discussed internally, and concluded that WTF should be postponed too.
We are very sorry for the late decision.
However, we hope to reschedule the event and hold WTF 2020 in the future.
We will announce the schedule again when the situation gets better.
AtCoder WTF 2020 will be postponed because of Corona Virus, Unfortunately, due to the new Corona Virus problem, we decided to postpone WTF
2020. In Japan
6.
Codeforces Round #201 Editorial 
Overview
========
In DIV 1, there are 4 interesting problems together with a normal one. We think it is reasonable because we can't have a round fullly with intelligence. Problem A, C have weak pretests while others intended to be strong. About more then 200 participants solve A in the early 45mins, then a few of them start from C while most of the other start from B.
Problem B is a rather standard problem, but if you're unfamiliar with the algorithm, it can be very hard. Problem C is a more intersting problem. As the name implies, there was [a similar version](http://codeforces.me/problemset/problem/251/C) in the previous round before, but this time it has a brand new constrains.(So here we have a psychology experiment: could different constrains make people thinking in a slightly different way?ww)
The standard solution of problem C is $O((b-a) + nlogn)$. The first expected correct solution was writt...
#### Analysis: This is a rather classical problem, let's say if there is no
virus, then it is the, ) #### Brief description: You have been given two strings $s_1$, $s_2$ and $
virus$, and you have to, When consider about the virus, we should add 1 more dimension on the state to
trace the growth of
Tutorial of Codeforces Round 201 (Div. 1)
Tutorial of Codeforces Round 201 (Div. 2)
7.
Simple Linear and Effectively Duval Algorithm for Lyndon Factorization --------------------
--------------------
--------------------
### <strong> <center style="color:red;"> Table of content </center> </strong>
| Teleporter | Description |
| :------------------------------------------- | :----------------------------------------------------- |
| [I. Lyndon Definitions](#lyndon) | Definitions of Lyndon word, Lyndon factorization, ... |
| [II. Duval Algorithm](#duval) | Talk about the duval algorithm and how it works |
| [III. Real Life Applications](#rla) | Motivation to learn the algorithm |
| [IV. Programming Applications](#application) | The code is short and simple to implement |
| [V. My Questions](#question) | Are there any other applications ? |
| ................................................................... |.............................
bacteria, virus.
8.
AtCoder Beginner Contest 133 English Solutions Since AtCoder often doesn't release English editorials to their beginner contests, I thought I'd write up my solutions. Feel free to add a comment if anything was unclear!
A — T or T
------------------
Our alternatives here are sending all $N$ people on the train, for a total of $N \cdot A$ yen, or using the taxi, for a total of $B$ yen. We should thus print the minimum of these two values.
Code: https://atcoder.jp/contests/abc133/submissions/6265526
B — Good Distance
------------------
We reword the problem slightly: for how many points $y$ and $z$ is $\sum_{k=1}^D (y_i-z_i)^2$ a perfect square?
Given the small input constraints, we know that this sum is going to be at most $10 \cdot (20-20)^2 = 16000$. Hence, we can simply compute a list of all perfect squares less than $16000$ and iterate over all $\dbinom{N}{2}$ pairs of points. For each pair of points, we compute the summation and check if it is equal to any of our squares. If so, we increment th...
; Virus Tree 2 ------------------ We build the tree from the top down. Root the
tree arbitrarily; we, E — Virus Tree 2 ------------------ We build the tree from the top down. Root
the tree
9.
International Odoo Programming Contest 2024 Editorial This is the editorial for the first edition of the [International Odoo Programming Contest](https://codeforces.me/gym/105056)
Author: [user:pauloamed,2024-03-27]
[problem:105056A]
<spoiler summary="Editorial">
Implement exactly what is being asked. That is, check if the input is a string of the format [email protected]:
- has @odoo.com as a suffix
- $S$ is size $2$, $3$ or $4$
- $S$ is composed only of lowercase letters
</spoiler>
<spoiler summary="Solution C++">
~~~~~
#include<bits/stdc++.h>
using namespace std;
int main() {
const string suffix = "@odoo.com";
string s; cin >> s;
int last_pos_at = s.find_last_of('@');
if(last_pos_at == string::npos || s.substr(last_pos_at) != suffix) {cout << "no\n"; return 0;}
if(last_pos_at < 2 || last_pos_at > 4) {cout << "no\n"; return 0;}
for(int i = 0; i < last_pos_at; i++) {
if(s[i] < 'a' || s[i] > 'z') {cout << "no\n"; return 0; }
}
cout << "yes\n";
}
~~~~...
(module position <= virus position) and the virus capacity is greater or equal
to the module, iterate over the viruses, if they collide (module position <= virus position)
and thevirus capacity
Tutorial of International Odoo Programming Contest 2024
10.
Lexicographically Minimal String Rotation --------------------
--------------------
--------------------
--------------------
--------------------
# <strong> <center style="color:red;"> Table of content </center> </strong>
| Teleporter | Description |
| :---------------------------------------------- | :----------------------------------------------------------- |
| [I. The Problem](#problem) | Describe about the problem |
| [II. Bruteforce Approach](#brute) | Simple way to do the problem |
| [III. Hashing Approach](#hash) | Reduce circular substring comparing complexity |
| [IV. Sqrt Decomposition](#sqrt) | Divide into parts, solve each part then solve the whole part |
| [V. KMP Approach](#kmp) | Magical Linear Booth-KMP Algorithm ...
bacteria, virus.
11.
Coronavirus — Overcome the Psychological Stress by Coding My video on the topic: [Shameless Self-Promotion](https://www.youtube.com/watch?v=CFagJwWW7ys)
Have you ever noticed how disasters have a weird way of making things better, once the initial problem is contained?
Yes, the virus is unpredictable, has deadly potential, and should be of great concern to just about every human on the planet. So, what could possibly be a positive consequence of a life-threatening disease?
#### _**1. Code (and live) for the present, not for that offer**_
Yes, these are not the best of times, but a time to reflect on who we are and what is most important in life. For some countries, economy is at risk. But most of Software Engineer jobs give you the opportunity to work remote/from home. Either you have or not a job at the moment, you are not so pressured by this thought anymore. Maybe you come to the conclusion programming is not what you want to do in life anymore. Maybe it's photography, cooking or pottery (Brad Pitt pff..).
Or maybe th...
problem is contained? Yes, the virus is unpredictable, has deadly potential,
and should be of great, the virus or what might come next. While a future-time perspective is also
helpful for human, Yes, the virus is unpredictable, has deadly potential, and should be of great
concern to just about
12.
Eertree (Palindromic Tree) — Comprehensive Resource Guide Hi Codeforces!
During Codeforces Round 1059 (Div. 3), I encountered **Problem E: Beautiful Palindromes**, which involves minimizing palindromic subarrays. While researching optimal solutions, I discovered the **Eertree (Palindromic Tree)** data structure — a powerful but relatively unknown tool for efficiently handling palindrome-related problems.
The Eertree can process all palindromic substrings of a string in **O(n)** time and space, making it ideal for problems involving palindrome counting, queries, and optimizations. However, I noticed there are limited and scattered resources for learning this data structure, so I've compiled this comprehensive guide to help the community.
### What is an Eertree (Palindromic Tree)?
The **Palindromic Tree** (also called **Eertree**) is a tree-like data structure that stores all unique palindromic substrings of a string efficiently. It was introduced by Mikhail Rubinchik and Arseny M. Shur in 2014.
**Key Properties:**
- Proc...
4. **Virus synthesis** [Codeforces
GYM](https://codeforces.me/gym/100548/attachments)
13.
ACM ICPC 2020 World Finals unacceptable rules Hi all!
I'm one of the 2020 (better to say 2021) wf participants, according to this [link](https://icpc.global/worldfinals/rules) there are two major differences between the upcoming WF and previous WFs:
- **Each team member will be provided with a computer.**
- **The competition is scheduled to last four hours.**
Obviously the first rule results in the second rule because when teams can write codes on three computers they are faster and so time should be reduced.
But the reason mentioned in the link for the first rule is " **Individual computers are provided for health safety purposes.** " which looks kinda meaningless.
The reason I say that, is that all team members which participate WF on-site are fully vaccinated, multiple times PCR tested people, and if they're infected by COVID, they will spread the virus between themselves in the hotel room they have to share or all the other places they are in touch together.
The only logical reason for the first rule (in my ...
infected by COVID, they will spread the virus between themselves in the hotel
room they have to share or, , multiple times PCR tested people, and if they're infected by COVID, they will
spread thevirus
14.
CodeDrills Beta Contest #3 [Team Contest] Announcement Hello Codeforces!
CodeDrills will be hosting its first team contest [CodeDrills Beta Contest #3](https://codedrills.io/contests/beta-contest-3) on [Sunday, 7th March, 2021 9:00 PM — 10:30 PM IST](https://www.timeanddate.com/worldclock/fixedtime.html?msg=CodeDrills+Beta+Contest+%233&iso=20210307T21&p1=438&ah=1&am=30).
There will be 4 or 5 problems to be solved in 1.5 hours.
**Contest Details**
- Contest Link — https://codedrills.io/contests/beta-contest-3
- Date & Time — [7 Mar 2021, Sunday, 21:00 IST](https://www.timeanddate.com/worldclock/fixedtime.html?msg=CodeDrills+Beta+Contest+%233&iso=20210307T21&p1=438&ah=1&am=30)
- Duration — 1.5 Hours
- Will follow standard ICPC scoring system (20 minutes penalty and 1 point per problem)
**Registration**
You will need to create a team on the contest page in order to participate. Team size can be upto 3. While creating the team, add the registered emails of other users to invite them to join your team. They will get an i...
practice - 1. https://codedrills.io/problems/new-virus-spread 2.
https://codedrills.io, ://codedrills.io/problems/new-virus-spread 2.
https://codedrills.io/problems/stack-of-boxes 3
15.
help in my code Phew, thank goodness you're back! During your absence, we observed some unauthorized data communication occurring from our storage warehouse. We promptly reported this to the chief since some data had already been stolen. The chief instructed us to trace the destination of the data theft. Our storage warehouse comprises individual data containers, arranged in an M*N matrix, with each container holding varying quantities of data represented as units. The containers are organized in M rows and N columns (with indexing starting from 1).
Our observation revealed that the virus consistently targets the container with the maximum data units. However, when two containers have equal data units, the virus's behavior becomes unclear, and we must avoid such scenarios. To determine the data's destination, continuous communication between the virus and the thief must occur. However, our priority is to prevent further data theft.
As the virus targets containers with more data, it always seeks ...
columns (with indexing starting from 1). Our observation revealed that the
virus consistently, containers, we aim to determine the minimum data required to be produced to
entice thevirus to the, fudging, it will became 12. 12 units of data will make it the maximum in
neighbourhood. Thevirus will, trap the virus with minimum amount of fudged data., where we want to entice the virus to., A total of 3+2 = 5 units of data was required to be fudged to entice the virus
to desired location., As the virus targets containers with more data, it always seeks neighboring
containers. It can, Next line consist of two space separated integers, indicating current location
of thevirus, Now the virus is on container [3,1], The neighbouring container of the virus
are [(2,1),(2,2),(3,2, Our observation revealed that the virus consistently targets the container with
the maximum data, Output The smallest amount of overall data needed to be fudged to attract the
virus to the dummy, The virus is on container [2,2] and we have to bring it to container [4, 1].
The neighbouring, We will add 1 unit of data to [2,2] so they virus will move there, Next we want
to move it to [3,3
16.
Hello your computer has virus: A case analysis how the current issues on CF and how to solve them Now I know what you're thinking...
"oh no. hes being racist again"
however, if you would so kindly look at any recent standings, especially ones which favour the timezone of indians... (like the last div1,div2 combined round...), you would notice quite the coincidence.
And if you think, oh well Codeforces is fucked... you would be wrong
Codeforces gets the short end of it, just look at meta hacker cup round 3, and compare it to any other year.
Now is calling out Indians racist? Without valid reasoning that they are the supermajority causing issues, yes. However, I believe I have valid enough reasoning. If the pure statistics don't convince you that we must target punishments towards India/bangladesh/pakistan?/basically that geographic region, then why not use logic instead?
Why do these people want to cheat? Well I've asked a few who obviously, I will keep anonymous. Simply put, its peer pressure. Somehow, most likely due to government corruption and other political things...
Hello your computer has virus: A case analysis how the current issues on CF and
how to solve them
17.
CP Editor 3.2 : CP Editor meets Competitive Companion Check : https://cpeditor.github.io
==================
Hi Guys !
You guys are truly amazing. I created CP Editor around 3 months ago just for fun and personal use, never wanted to make it public but anyways, I decided to make it public with [this blog](https://codeforces.me/blog/entry/71673). I got so much love and support that I could not hold myself back from improving it, in following weeks I released the second version in [this blog](https://codeforces.me/blog/entry/71907). Fixing a lot of issues and bringing new features.
Let's get into what is new in this release of CP Editor. But first,
#### Merry Christmas programmers!!
Thanks to [user:ouuan,2019-12-25] for his wonderful contributions. Almost all new features were implemented by him.
#### What's New
- [**NEW**] Save and restore Input and Expected outputs. Highly requested by [user:IWanna_MightiestDisciple,2019-12-25] [user:ekalavya_k_k_p,2019-12-25] [user:smile_,2019-12-25] [user:Double_Helix,2019-12-25])
...
for the port in your Anti-virus or firewall settings., listening or request from arriving, you may need to add an exception for the
port in your Anti-virus or
18.
Editorial for CCxEnigma: Tesseract '26 (IIIT Vadodara) Tesseract '26 Editorial
==================
Hello Everyone!
Hope you enjoyed **[CCxEnigma: Tesseract '26](https://codeforces.me/blog/entry/150726)** conducted by [IIITV Coding Club](https://iiitvcc.vercel.app/home) and Mathematics Club at IIIT Vadodara.
Thank you for participating in the contest. Hope you had fun solving the problems with the new Sandbox twist :)
This was the first time a reverse coding event was hosted in this **style**!
_Feel Free to give some feedback in comments whether you **liked** it, suggestions for **improvement**, or ideas for the **Next** Edition :)_
Here are the official tutorials for the problems.
Access the Sandbox here — [_SANDBOX_](https://tesseract-2k26.vercel.app/sandbox)
### [Problem A: DDR4 Shortage](https://codeforces.me/gym/668703/problem/A)
Author: [user:Mr.Quantum_1915,2026-02-01]
<spoiler summary="Hint">
Try entering aa and aaa in the sandbox.
aa (Length 2) $\to$ 2a (Length 2). No space is saved, so i...
The virus spreads $K$ units in both directions. This means any person, $, you get infected. The virus spreads $K$ units in both
19.
Explanation and Solution of 1689-C in Python [problem:1689C]
The approach I am sharing here uses the Greedy-Algorithm and BFS for tree-traversal.
It's obvious that we'll start deleting nodes from the top. Observe that in each operation in which we delete a node, the virus would infect at most 1 more node. To save most nodes, virus propagation has to be stopped using minimum deletion operations.
The question is, when does virus propagation stop?
It stops in either of the cases:
1. The virus has reached a leaf node.
2. The virus reaches a node which has a single child (In this case, as soon as the virus reaches such a node, we'll delete it's child and then the virus will have nowhere to propagate)
So, the question essentially is to be able to find either of the above 2 types of node which is closest to the root.
The number of nodes saved in the 1st case would be n-2*l+1 and in the 2nd case, it would be n-2*l. You can verify this by taking examples. (n=number of nodes, l=level in the tree at which such a no...
we delete a node, the virus would infect at most 1 more node. To save most
nodes,virus propagation, which we delete a node, the virus would infect at most 1 more node. To save
most nodes,virus, 1. The virus has reached a leaf node., 2. The virus reaches a node which has a single child (In this case, as soon as
thevirus reaches, The question is, when does virus propagation stop?
20.
Morocco Refuses to Host African Cup of Nations 2015 Due to Ebola Virus. What
about ACM-ICPC WF 2015?
Morocco Refuses to Host African Cup of Nations 2015 Due to Ebola Virus. What about ACM-ICPC WF 2015? Hello,
I'm really starting to think that plans to host ACM-ICPC World Finals bring misfortune. ACM-ICPC World Finals 2011 initially were planned to be in Egypt, but revolution has changed plans.
What do you think about chance to drop World Finals in Morocco because of Ebola Virus?
Morocco Refuses to Host African Cup of Nations 2015 Due to Ebola Virus. What
about ACM-ICPC WF 2015?, . What do you think about chance to drop World Finals in Morocco because of
EbolaVirus?, What do you think about chance to drop World Finals in Morocco because of Ebola
Virus?
21.
Is Hello Muscat postponed? Recently, I saw a tweet from Phaza Ventures, a local sponsor of Hello Muscat:
Dear Participants,
As the Corona Virus is still spreading, and to ensure everybody's safety, we have decided to postpone the Bootcamp to later dates to be announced.
Sponsored by:
@BP_Oman
Event Organizers:
@ukomandigihub @Harbour_Space @GUtech_CSC
Local Host: @GUtech_Oman
https://twitter.com/PhazeVentures/status/1236923603368755200?s=19
As I understand, the bootcamp is going to be postponed.
, As the Corona Virus is still spreading, and to ensure everybody's safety, we
have decided to, Dear Participants, As the Corona Virus is still spreading, and to ensure
everybody's safety, we
22.
OA Question Discuss There are n servers where the ith server can serve request[i] number of requests and has an initial health of health[i] units.
Each second, the developers send the maximum possible number of requests that can be served by all the available servers. With the request, the developers can also send a virus to one of the servers that can decrease the health of a particular server by k units. The developers can choose the server where the virus should be sent. A server goes down when its health is less than or equal to 0.
After all the servers are down, the developers must send one more request to conclude the failure of the application.
Find the minimum total number of requests that the developers must use to bring all the servers down.
constraints :<br/>
1<=n<=1e5 <br/>
1<=req[i],health[i]<=5e3<br/>
1<=k<=5e3<br/>
example =<br/>
n=2<br/>
k=3<br/>
req=[3,4]<br/>
health=[4,6]<br/>
<br/>
ans = 21
<br/>
can you share your approach for this problem. I didn't get idea how ...
virus to one of the servers that can decrease the health of a particular server
by k units. The
23.
The Role of Randomness in Problem Solving and Creativity Randomness often plays a crucial role in various problem-solving strategies, such as the hill-climbing approach. In this strategy, you start by identifying a local maximum—an optimal solution within a limited scope. From this point, you have two choices:
1.Use this local maximum as a base to explore more optimal solutions.
2.Intentionally deviate from your current choice, allowing for the possibility of discovering better solutions more quickly.
This journey from more randomness to less is akin to elongating a path until we arrive at a final solution. Interestingly, if we rush the process, the final outcome may differ significantly from one achieved through careful exploration.
Consider the analogy of planning a trip through ten cities. While the number of cities seems manageable, the permutations involved—10! (10 factorial)—reveal just how complex the task can become.
Moreover, some physicists, including an Italian researcher from Indiana University, have highlighted th...
24.
Codeforces Round #201 (Div. 1)<B. Lucky Common Subsequence> http://codeforces.me/contest/346/problem/B
classical longest common string problem(LCS), dp algorithm
classical string matching problem, kmp algorithm
solution:
First,for LCS, dp[n][m]=
dp[n-1][m-1] ;if two char match
max(dp[n-1][m],dp[n][m-1]) ;if two char not match
then, there is virus
dp[n][m][k]=
dp[n-1][m-1][k-1] ;if all three char match
dp[n-1][m-1][fk] ;if only two char match, fk start over
max(dp[n-1][m][k],dp[n][m-1][k]);
dp[n][m][k] means the virus after k is all matched, so if k <0 then all virus matched, which is invalid.
for the equation dp[n][m][k]=dp[n-1][m-1][fk] ;if only two char match, fk start over
just two char match, so the virus must has to start from the beginning, but may not real beginning.
strA: BCBC
strB: BCBC
virus:ACBC
when matching from the right to left, and meets (B,B,A), although matching failed at A, but there is still has a matching string of 'BC', we just not need to start from the real begining. Where t...
char match, so the virus must has to start from the beginning, but may not
real beginning. strA: BCBC, is virus dp[n][m][k]= dp[n-1][m-1][k-1] ;if all three char match
dp[n-1][m-1][fk] ;if, ][m-1]) ;if two char not match then, there is virus dp[n][m][k]=
dp[n-1][m-1][k-1] ;if all
25.
Help on Problem 346B Hello, Codeforces:
I worked on problem [346B](http://codeforces.me/problemset/problem/346/B) for a long time, and I could not come up with solution. Even when I read editorial and comments, the solution is still unclear to me. I know, it is KMP + DP, but I cannot see what KMP should be used on, DP transitions, etc. I know in the dp[i][j][k], i and j represent indices in str1 and str2, and k represents the longest match of the current subsequence and virus, but I cannot really get anything else.
I have worked for a few hours, but I don't have really much progress, and editorial/comments doesn't really help. So if anyone could give a clear explanation of this problem, it would be great and I would much appreciate it.
Thanks,
minimario
match of the current subsequence and virus, but I cannot really get anything
else., represents the longest match of the current subsequence and virus, but I
cannot really get anything
26.
An idea about code forces anti cheat system An idea about code forces anti cheat system
Hi guys , so after reading that a channel on youtube post solutions to problems i got really mad , this will cause credibility of codeforces damaged and also will cause rating inflation if it's continues.
So I think the problem should be taken seriously , and I have an idea. Why not use the same idea that game companies use?
So I know most people know how they are working , first of all cf cant use IP ban since you can change it easily , but cf can use HWID ban.i know i know there are some softwares that can spoof HWID too but most of them are fake and contain virus in them and even if one of them work i have an idea for that too.
So my idea is that we should download a local program that runs on our computer which we should submit our solution with that software to cf servers. This software will keep track of your username and HWID , you can have increasing rating if your HWID that you registered stays the same so if a person creat...
are fake and contain virus in them and even if one of them work i have an idea
for that too. So my, too but most of them are fake and contain virus in them and even if one of
them work i have an idea
27.
The Beginning Well given that this corona virus made me a lot more free time than usual, i've decided to have a try at these algorithm competitions. My blog will be mainly be for discussing contests that I will take part in (both live and virtual participation) so I can track my progress.
Currently I participated in two contests ([link](https://codeforces.me/contest/1326), [link](https://codeforces.me/contest/1325)) and have been rated 1500 (whatever that means). I'll make my current goal to focus more on solving more than 3 problems in each contest and improve my knowledge on specific algorithms so we will see how that goes. Hopefully I will be able to do at least one competition each day in the next week and see how it goes from there.
Well given that this corona virus made me a lot more free time than usual, i've
decided to have a
28.
April Fools Day Today is the April Fools Day. We fool corona virus by keeping social distance, washing hands, wearing masks, etc. Meanwhile, I suggest to share some c<s>f</s>ool jokes and d<s>umb</s>ank memes here!
Today is the April Fools Day. We fool corona virus by keeping social distance,
washing hands
29.
Can't wait 9days for the contest I have diagnosed with waittingo-contestino virus. To cure that I need to join a **codeforces** **contest** asap. please MikeMirzayanov, can't wait for 9 days ( I might die in 9 days. :( ).
I have diagnosed with waittingo-contestino virus. To cure that I need to join a
**codeforces
30.
BFS DP problems? There are some few problems I came across like [Fish](http://codeforces.me/problemset/problem/16/E) and [Virus synthesis](http://codeforces.me/gym/100543) which seem to have solutions with BFS traversal and typical DP minimization/maximization function. I want to practice this technique because normally when I think of coding a DP solution I only think of DFS traversal, any ideas of problems which are best solved using this technique?
EDIT: Just a clarification this DP style is usually a "Reverse" BFS Traversal of the states where we travel from the leaf nodes upwards level by level and converge to the final state
) and [Virus synthesis](http://codeforces.me/gym/100543) which seem to have
solutions with BFS
31.
Computer Virus Codechef Problem Hi Everyone!<br>
I am trying to solving this codechef [problem](https://www.codechef.com/problems/CMPVIRS).<br> I am stuck in the theoretical mathematics part of it.<br> The [editorial](https://discuss.codechef.com/questions/125361/cmpvirs-editorial) explains some equations which i am unable to understand. <br>
Can somebody please explain me how these equations are formed and worked along and where does this algebraic representation of pascal triangle given in the [editorial](https://discuss.codechef.com/questions/125361/cmpvirs-editorial) come from?<br>
Any help is appreciated.<br>
Thanks.
Computer Virus Codechef Problem
32.
Copilot is an evil virus of Satan 
Abandon thy false gods; Copilot will not save thee.
Copilot is an evil virus of Satan
33.
Code Forces Round 201 B Lucky Common Subsequence strongly question For this question：codeforces 201B Lucky Common Subsequence。
it ask us just one virus so we can use kmp + dp to solve this question。
but i have a question that if ask us more than one virus what should i do？？
i have an ideal just use Aho-Corasick automaton to get fail array but i do not know how to set dp array？
Can anyone help me ?
Thanks in advance!!
For this question：codeforces 201B Lucky Common Subsequence。 it ask us just one
virus so we can use, but i have a question that if ask us more than one virus what should i do？？ i
have an ideal just
34.
Teams going to Gwalior/Pune Regionals **UPDATE:**
I've uploaded the code that I used to generate this on Github, in case someone needs to generate something similar:
[Codeforces Team Rating Calculator](https://github.com/abdullah768/Codeforces-Team-Rating-Calculator)
The regional round has ended and here's the final Ranklist:
https://www.codechef.com/public/rankings/ACM18GWR
Inspired by the list of teams going to Kharagpur regionals, I decided to make one for Gwalior/Pune regionals. The list contains all the teams from the official Gwalior website. If you know the usernames of members of any of the teams. Please update the excel file:
### [HERE]
(https://docs.google.com/spreadsheets/d/1jRvwzQzp1DOcazgI7jXBB8uY3u7Ze_eQ77Xa75_Q810/edit?usp=sharing)
Team rating calculation has been done according to the official Codeforces team rating calculation formula.
The table will be updated with details from the excel file every 6 hours or so.
Last Updated: 10 pm, 12th December IST
| No. | AIR | Team Name ...
| ViRuS
35.
brute_force Accepted 100543 G(Virus synthesis), I definetly don't know what is the time comlexity,seems to be O(n^2) http://codeforces.me/gym/100543
can't believe my eyes.....
brute_force Accepted 100543 G(Virus synthesis), I definetly don't know what is
the time comlexity
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