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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.
How to practice Competitive Programming [Um_nik version] CP is about solving problems fast. And as absurd as it may sound, I believe that <span style="color:blue">SOLVE</span> and <span style="color:red">FAST</span> are very different and almost independent parts, and you need to practice them separately.
Let’s look at some <span style="color:red">contest</span>, like a CodeForces round. For the sake of simplicity let’s assume that every problem has some *difficulty*, which is a numerical value denoting how hard it is, bigger values correspond to harder problems (it is not true, but it is an ok-ish approximation, at least if we consider subjective difficulty for a fixed person). Contests are made for a wide range of participants, and problemsetters strive to make contests interesting for a wide range of participants, which means having a *smooth difficulty gradient*. Well... as smooth as it is possible with 5-6 problems.
<spoiler summary="Graph 1">
2.
How to get 100% points for hackerrank challenges with inadequate solutions In this post I will describe inadequate solutions for 4 hackerrank problems from last 2 codesprint contest, that I participated(with difficulty hard-advanced), that get 100% score and provide counter-test to each solution.
[**NCR Codesprint, Coconut Plantation**](https://www.hackerrank.com/contests/ncr-codesprint/challenges/coconut-plantation)
At first we will water plants, as described in official editorial:
For example, we need to water squares (2,2,3,3) and (3,3,4,4). We add one to the highest cells of this square and decrement one from cells under this square. After we do this with all rectangles, we can get array of watered coconuts by simple cycle:
~~~~~
for (int i = 0; i < r; i++)
for (int j = 0; j < c; j++)
b[i][j] = (i>0?b[i-1][j]:0) + a[i][j]; // a[i][j] is array from the picture
~~~~~
We got array b and now we change values of b[i][j] to 1 if b[i][j] >= m else to 0.
In official editoria...
attention to this comment, you will see this sentence: `"Problemsetter of last
problem said that he, see this sentence: `"Problemsetter of last problem said that he will change
the test cases, because I
3.
How to read problem statements But [user:Um_nik,2018-10-26], we all know how to read, we have our whooping 2 month of experience! Oh, my sweet summer child, my experiments show that many people with kinda cool achievements like medals on ROI don't know how to read statements. But don't worry, I'll teach you. Well, probably you won't understand anything, because you didn't try to understand anything in your life, you expect all hard work to be done for you by someone else. Let's start!
Basic rules
==================
- The result of reading the statement is usually pure math model. If story helps to build correct understanding, you can keep it, but still try to discard as many unnecessary details as possible.
- Imagine you want to tell the problem to someone else. What parts you want to tell? (According to my PM, this rule won't help you).
- Shorter = better.
- Simpler = better.
- Limitations are part of problem statement. Especially small limitations, because for small data you can try all the possib...
me, since I'm a bad problemsetter? I don't know, maybe you shouldn't. Some
examples
4.
Let's face it, Polygon is horrible 
Polygon is not world's greatest evil. Polygon doesn't even have a particular defect that makes it horrible. You can't say what's exactly wrong with Polygon. Polygon seems to work, it seems like every feature is supported, but if you touch it here it will fall apart, and if you touch it there a problem (pun not intended) will appear. Or not, depending on your luck. Polygon is like PHP. For those who haven't read the famous rant, I'll cite it for you:
> I can't even say what's wrong with PHP, because-- okay. Imagine you have uh, a toolbox. A set of tools. Looks okay, standard stuff in there.
>
> You pull out a screwdriver, and you see it's one of those weird tri-headed things. Okay, well, that's not very useful to you, but you guess it comes in handy sometimes.
>
> You pull out the hammer, but to your dismay, it has the claw part on both sides. Still serviceable though, I mean, you can hit nails with the middle of the head holding it...
return and 'Want to run solutions?' magically starts to work. But then Rejudge
of theold invocation, work. But then Rejudge of the old invocation breaks. Yet it works on another
solution. Screw you, you
5.
Changes in CodeChef Problemsetting Hello Codeforces!
For the last half a year I have been working on CodeChef and was proposing ideas on how to change the problemsetting practices (hopefully, for the best). For some time the changes were in brainstorming phase, but as of now many of them are implemented. Today we are ready to share the information with you. But first I would like to approach people who are going to close this blog without reading:
If you are not interested in CodeChef contests at all, I think you should change your mind. Monthly short contests (Cook-Off and Lunchtime) have interesting quality problems, on par with Codeforces in my opinion (not AtCoder level yet, but who are?). Long and Starters are more targeted to newbie participants, with more classical educational problems.
If you are interested in setting problems for regular contests, you might want to do it on CodeChef. Some reasons:
- You don't have to set the whole round, as we work on per problem basis.
- This may be especially...
-04e997a2943d43cdbb04a05a09669085). It's very new, but at least there are links
to all theold guides I
6.
A proposal to change to open hacks on normal rounds Hacking has always been a hot issue and many people had mixed feelings on it. While I personally love the concept of hacking, I should agree that hacking on normal rounds is not very functional nowadays and is only causing several issues.
- **The concept of rooms is heavily luck-based.** Depending on one's luck, there may be 0 to several submissions that can be hacked, and it is unfair to give several hundreds of free points to those who get a jackpot room. Even for the ones who submitted a wrong solution that passes pretests, it requires luck for them to be hacked by someone else so that they can realize that the solution was wrong and resubmit.
- **Image blurring is not effective.** Although by the rules using OCRs to convert the images to texts is prohibited, there is no way to know if one is using them or not. In the old days, even if someone uses them we may have thought that it won't be very accurate, but nowadays OCRs are just too good and only the honest people who don't us...
know if one is using them or not. In the old days, even if someone uses them
we may have thought that
7.
UVA problem seemingly above the State of the Art I stumbled upon [UVA Summing the Lengths of the Longest Increasing Subsequence of Permutations](https://uva.onlinejudge.org/index.php?option=onlinejudge&page=show_problem&problem=2247), that basically asks for the first three digits of the sum of the LIS lengths over all permutations of length $n$. After trying it or a few days, I gave up and searched for information. It is easy to see that:
$$\sum_{w\in permutations(1,2,..,n)} LIS(w)= \mathbb E(LIS(w))\times n!$$
Where $\mathbb{E}$ denotes the expected value. It is easy to manage the logarithm of that number with Stirling's approximation, get the fractional part of the logarithm and exponentiate to get the first digits. Nevertheless the core of the problem lies in computing $\mathbb{E}(w)$ for a random permutation $w$ of length $n$. I have been reading about the topic, and [this paper](http://stanford.edu/~mikep15/mike_math310_report.pdf) gives the estimate
$$\mathbb{E}(w)=2\sqrt{n}+cn^{1/6}+o(n^{1/6})$$
Where $c\approx -1.77108$ ...
am right now trying to contact the problemsetter [user:baodog,2015-10-11]
looking for clues, as, strange too, since the only accepted solution's are Josh Bao's(the
problemsetter) in the $2007$ and
8.
[Invitation] IICPC CodeFest 2025 ### Greetings, Codeforces Community!
We are thrilled to invite you to **CodeFest**, a premier competitive programming event brought to you by [IICPC](https://iicpc.com/), co-sponsored by [Citadel](https://www.citadelsecurities.com/) and [Jump Trading](https://www.jumptrading.com/), Associate sponsors as [Jane Street](https://www.janestreet.com/), [Hudson River Trading (HRT)](https://www.hudsonrivertrading.com/), [Landeed](https://www.landeed.com/) and [QuantInsti](https://www.quantinsti.com/) being the Knowledge Partner.
The camp is being hosted by the 8 IITs namely Madras, Delhi, Bombay, Guwahati, Hyderabad, Kharagpur, Roorkee and Indore and we are grateful for the same!
You can check our event announcement video [here](https://www.youtube.com/live/cKTUU0PEBYA?si=eEwZ0iiLaeiYkdM4).
---
### **Inspiration**
In late 2024, Ayush and I were wondering what could be done next to improve the Competit...
. Note : Pls clear cache if old website of IICPC is visible. The new website
mentions Codefest 2025
9.
The inevitable despair of a fallen man, a truly demotivating rezil story Hello CodeForces, tonight we mourn the sad demise of a man who once was a legend, truly an icon in the Turkish CP community. That man is [user:AhmetKaan,2025-09-21] Avcı. Let me tell you the sad, disgusting story of how he became who he is and what has yet to happen to him.
Our story begins in 2004, just two days ago in September 19th. Born in Kastamonu/Türkiye to a family of 6 children, a family that posseses one IMO participant (Ömer Avcı), and one older brother who once dominated Turkish Olympiad programming. ([user:farukkastamonuda,2025-09-21] orz) This man was obviously blessed with inspiration from an abundance of role models inside his own home. Even though genetics seemed to be to his advantage, he always lacked the skill to even do simple math. He cried his nights yearning to become like his elite brothers. It just didn't come natural to him, ever.
His prayers were answered and his older brother Faruk came back home from his highschool outside Konya, and trained him al...
years, acting as a problemsetter and an instructor. Jokes aside he is without
doubt one of the most
10.
New Year wishes from participants — "Cyan Rebellion 2022" survey results Hi! Two weeks ago I made a survey [link here:](https://codeforces.me/blog/entry/98424) about making Codeforces better. In this blog I am sharing the results. Consider reading the previous blog first, but this one should be self-contained as well.
TLDR
------------------
The quality of Codeforces problems has increased over time, and people are mostly happy. Participants would probably be even happier with a greater variety of problem topics. It's important for setters to consider the contest as a whole, including the target audience of a given task. Some users wrote essays longer than the entire survey.
How to access the results
------------------
Before we start, I would like to invite everyone to take a look at the raw data. If you are keen on showing off your data analysis skills, please do so! I hope that some of us will manage to find more interesting insights taking into account preferences of users from various skill groups.
[Raw results](https://docs.google.com/...
outcome arises from the "Problem target" question. If you are a problemsetter,
please consider
11.
Problemsetter's Memoir Preparing a contest is not as popular a topic as the perennial question of "how to become red in three months", but still it stirs some interest in Codeforces community now and then. Earlier I've written about [preparing Surprise Language Round](http://codeforces.me/blog/entry/4290) and about [emotional aspect of problemsetting](http://codeforces.me/blog/entry/3857); now it's time to share some facts about running regular contests.
### Problems
> How much time does it take to prepare, select, recall or find problem ideas?
> How much experience solving competitive programming problems is necessary to be confident about inventing problems of your own?
Idea generation is a long-term, nearly continuous process. A couple of years ago when I was still an active problemsetter I used to create ideas from literally everything (a squirrel running... hey, this could be a great problem! — seriously, the problem is still there in my drafts, and a pretty comp...
active problemsetter I used to create ideas from literally everything (a
squirrel running... hey, this
12.
Cormen Medal Laureates 2010 <img src="http://assets.codeforces.com/images/medals.gif" style="float:left;margin:0.5em 1em;width:150px;">
<p>
The year 2010 is over and of course, we are all ready not only to meet the Old Style New Year, which is a Russian national holiday. We are also ready to learn the names of those awarded by the Cormen Medal in 2010.
</p>
<img src="http://assets.codeforces.com/images/tourist.jpg" style="float:right;margin:0.5em 1.75em;width:140px;">
<p>
First, nomination "The Best 2010 Secondary School Contest Participant". And the winner is... (drum-roll) <a href="http://codeforces.me/profile/tourist">Gennady Korotkevich</a>. He took part in 5 out of 6 WPS (Winter Programming School) Olympiads organized by the Codeforces and won each of them! He participated individually in the team contest, but nevertheless got ahead of all the contestants.</p>
<p>
The Cormen Medal in &quot;The Best 2010 Participant" nomination gets...
<a href="http://codeforces.me/profile/tourist">Genna...
:150px;">
The year 2010 is over and of course, we are all ready not only to meet the Old
13.
What makes a good Div2A? As a [problemsetter](https://codeforces.me/blog/entry/147831), this is a question that I've been thinking about for a very long time — writing high-quality and challenging tasks for a contest's problemset is a valuable and much-discussed skill, but barely anyone ever talks about or even remembers the first two problems of a contest (barring Div1s, which this blog post largely doesn't apply to). This is a great shame in my eyes; Div2As always boast the highest solve counts in virtually every Div2 round, and are accessible to the widest audience of Codeforces users, but are almost never discussed in the comments section of the contest blog post or editorial.
Is this simply because such tasks are considered trivial in the eyes of most Codeforces users (at least, those rated above 1200) and therefore not worth discussing? Perhaps, but there are usually about two to four thousand people per contest who solve the Div2A and Div2B but fail to solve anything beyond that, meaning that...
As a [problemsetter](https://codeforces.me/blog/entry/147831), this is a
question that I've been
14.
Some thoughts about Surprise/Unknown Language Rounds I'm a huge fan of Surprise/Unknown Language Round competition format. Theoretically I enjoy participating in them, but in practice I mostly run them.
What's so special about them that makes me like them so much?
1. They are unusual. At some point of time (which arrived pretty soon for me) traditional competitions pall and become a blur. If I give it a thought,
I can clearly remember only a couple of the 80 SRMS and CF rounds I've done. The SRM which featured MooresLaw problem (great challenge phase and my only ever
room win), TCO elimination round which I passed thanks to a last-minute submission on 500pt, a GCJ round from back when it was held on TopCoder platform, when
I got stuck at input parsing and never got to the actual solution... and that's all. Marathon memory is a bit better, probably because I've participated in
fewer of them, and each match took more time and effort. But unusual competitions leave the most lasting and vivid impression.
2. They fit my skills....
enough to pick a fancy language for that --- you'd also need a problemsetter
who will choose it, good old algorithmic problems with a twist in syntax and library functions ---
and that's not what you
15.
Run-twice (aka communication) problems with Polygon and testlib.h ### Introduction
_Run-twice_ problems (also called _multipass_ or _communication_ problems) are problems in which your program is executed twice. Here are some examples:
- [problem:2054A] from the TON marathon.
- Problems D, G and K from [Universal Cup Season 2 Stage 5](https://assets.ucup.ac/statements/statements-2-5.pdf).
- All problems from [Universal Cup Season 2 Stage 16](https://assets.ucup.ac/statements/statements-2-16.pdf).
- [Flash](https://boi2019.eio.ee/wp-content/uploads/2019/04/flash.en_.pdf) from BOI 2019 (this one is actually more complicated, but the premise is the same — there are multiple instances of your program which cannot share data except through the interactor.
As you can see, there are many ways this format can be used, but the common themes are encoding/decoding, compression/decompression, constructing a bijection and similar ideas. The general principle is that you have to implement two functions and the second function has to somehow use t...
, the problemsetter — test inputs and data printed by your programs. Orange
arrows denote data
16.
First season HNOI Civil War conclusion _Dear Codeforces community,_
Lately, we have successfully organized a high-schoolers' contest: HNOI Civil War. The contest was born as a "rivalry" between two of the best Hanoi-based gifted high schools: Hanoi-Amsterdam High School and Nguyen Hue High School. 3-people organizing committee includes: Trung Lan Nguyen ([user:lantrungseo,2019-07-21]) — as the Head Organizer, Bao Quoc Ngo ([user:b21quocbao,2019-07-21]) — as the Head Problemsetter and coach for Nguyen Hue informatics team for this contest, and me, Dung Tuan To [user:low_,2019-07-21] — as the Head Coordinator and coach for Hanoi-Amsterdam team.
[cut]
.
The competition consists of two contests: an Individual-based OI-formatted round and a Team-based ACM-formatted round. You can visit the rounds as information listed below:
- **Individual Round One** _(July 14)_: written by low_ and lantrungseo, consists of 4 OI problems:...
([user:b21quocbao,2019-07-21]) — as the Head Problemsetter and coach for
Nguyen Hue informatics
17.
Busy but Master #la finale Alternative name: "Road to Master when you don't have time".
Episode 1: [link](https://codeforces.me/blog/entry/133458)
Episode 2: [link](https://codeforces.me/blog/entry/134585)
Episode 3: [link](https://codeforces.me/blog/entry/135821)
Chat is this real? [You've done it.](https://youtu.be/YPgmpR2WtdM?t=33)
I still feel like a looser. 2102 is a worthless rating. If I only had 2200 — that would be a completely different story.
#### Practice results (03.08.24-12.01.25)
* Rating: 1717 -> 2102 (+385)
* Min-Max Rating: 1612 -> 2102 (+490)
* Top rank: [39](https://codeforces.me/contest/2022/standings/participant/193771259#p193771259)
* Virtual rating: [2132](https://codeforces-anytime.sonoapp.page/users/EbhjfE7PgSObRdcmppn7dzpxsJr1)
* Solved problems: 963 -> 1334 ~= 371
* Contests official: 27
* Max delta: [+163](https://codeforces.me/contest/2022/standings/participant/193771259#p193771259)
* Min delta: [-136](https://codeforces.me/contest/2030/standi...
goal. The point is to compare ourselves with our old selves. * Ranks. Split a
goal to milestons
18.
On Div2ABs 2 years ago, [user:antontrygubO_o,2022-04-27] wrote [a blog](https://codeforces.me/blog/entry/75163) about div2ABs where he expressed his opinions that d2ABs should not be about "here is a statement, please implement what is written there". Thanks to him, the quality of d2ABs (and problem quality in general) have certainly improved. However, I still believe that there still quite large differences between how coordinators/problemsetters view d2ABs and how the intended participants view them.
From the survey made by [user:kpw29,2022-04-27], we can see that most people agree that most people agree that we should **primarily** consider the target audience when proposing a task. I too think if a task is boring to div 1 contestants, we should not think of that as a reason to immediately disqualify a problem from being a d2A.
I think when people judge the interesting-ness of d2As, they try...
, it would be best if a 5 year old can read the statement and be able to
understand the problem
19.
Codeforces Round 987 (Div. 2) Editorial <spoiler summary="A little backstory about the round (ACGN)">The Highschool CPers (HSCP) Discord server was created in April 2022 by [user:pwned,2024-11-14], which over time grew into a close-knit community of highschool competitive programmers. I joined in the same month of its creation, and in the next month I approached [user:pwned,2024-11-14] about the possibility of setting a contest. Thus the HSCP round concept was born.
Over the next month or so, the initial problems were born; the current problems A and F were produced in June-July 2022. We had several problem ideas by then, enough to set a div.2 round. However, as I was going to be busy in my 5th year of high school, and may not be that responsive to coordinators, the contest was in the ownership of [user:pwned,2024-11-14], who needed to wait until he reached master in order to propose the set on Codeforces.
However, this step took almost 1.5 years as he would stay at candidate master for 57 consecutive contests, eve...
proposals — around 30 of them. I looked through my old proposals — problems
written by me 2
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