I waited for more than a year to write this blog.

I started CP in July 2017, I always dreamed about reaching red, and it finally happened. I didn't become red like talented contestants in 1-2 years, but it took me more than that.

The start of my CP journey was average (you can see my graph); It took me more than six months to reach pupil, then another six months to get specialist, and it took me more time to achieve higher ranks. I didn't have any mentor or coach. So, I asked many stupid questions, which you can find if you read my old blogs. One of these questions is, "What's the importance of Dynamic Programming?" (I drafted this blog xD), But of course, I don't motivate people to ask these types of questions as they usually can be answered by just searching.

I failed many times during my journey in CP, especially in important competitions (IOI21 and IOI22). I stopped CP many times because I was frustrated and believed I could never improve. For example, I stopped when I was a pupil because I was frustrated that I would never be a stable specialist, but then I returned to CP and decided to try again.

I want people who are stuck in the newbie or higher ranges for much time to know that if you are stuck for a long time in your rating range, it doesn't mean you can't reach higher ranks. It's normal to be stuck for some time in your rating range. What's wrong is comparing yourself with your peers, as everyone starts with a different problem-solving background.

I wrote this blog to show people that no matter how many times you fail or how much time you're stuck in your rating range, there's a light at the end of the tunnel if you keep practising. It's okay to fail many times and to have time before improvement. Don't get frustrated because of some bad contest results. Instead, Analyze what's wrong in your training and fix it. Lastly, I want to show that red isn't impossible and anyone can reach red with enough practice.

I emailed IZhO23 two months ago asking about details for IZhO23, and they finally replied.

IZhO23 will be an online event for international contestants on 1 — 10th February, but it will be an onsite event for Kazakhstani contestants on 1 — 4th February.

The participation fee for every contestant is 50$, and the deadline is on 30th December. For more info, see IZhO website.

Good luck to everyone participating :D.

Hello Codeforces,

I'm a member of the Egyptian IOI 2022 team, and I'm not sure yet if we are going to IOI. Historically, the Ministry of Communication and Information Technology (MCIT) sponsored the Egyptian team to travel to IOI. However, this year, there is no confirmation from the MCIT's side at all. Our tickets are not booked until now, and MCIT doesn't either confirm or deny that they will sponsor us this year.

Now, there are fewer tickets left, and the cost of traveling increases as we approach IOI. We all have been practicing really hard for IOI for the past few months. Now, there is very little time for us to make alternative plans to participate onsite.

Note that MCIT provides training and sponsors the team every year so we expected more from the MCIT side. AASTMT has supported us with a part of ticket expenses

In an attempt to collect the remaining part, we created a crowdfunding campaign. Please donate here.

UPD: We've reached the crowdfunding campaign goal. Thanks to CF community.

Hello codeforces,

We've seen some crowdfundings campaigns on codeforces in the recent years, Mostly about covering travel expenses to IOI, For example:

• Egypt's IOI2018 team published a crowdfunding campaign in this blog to cover travel expenses to IOI18, and they received 145% of their goal (4,000$) in just a few days.

• Ukraine's OI published a crowdfunding campaign in this blog to cover the costs of holding an onsite qualification to IOI22, and they received 104% of their goal (goal was 7,292€) in 1-2 weeks, I believe.

• Greece's IOI2022 team published a crowdfunding campaign in this blog to cover travel expenses to IOI22, and they received 130% of their goal (goal was 12,000€) in 1-2 weeks, I believe.

however, Tunisia's IOI2022 team published a crowdfunding campaign in this blog to cover travel expenses to IOI22 but they received no funds from codeforces! (Here's the donation link).

I believe the Tunisian team (like the Greek team and any other team) deserves to compete onsite in IOI22. Participating online in IOI is pointless because you miss the entire event and only compete in the contest online, making it feel like any other online contest, and they can't find a sponsor because their country is experiencing economic difficulties as a result of the COVID-19 pandemic.

I'm curious why the Tunisian IOI2022 team didn't receive any funding from codeforces community; I initially assumed it was because their crowdfunding was done on a Tunisian website, but I don't think that's the case because the Tunisian website is safe and Ukraine's OI crowdfunding was done on a Polish website and they were successful in reaching their goal. This case appears to be similar to the Greek IOI22 team, but they were successful in reaching their campaign goal. If anyone wants to contribute Here's the donation link, any help would be much appreciated.

I couldn't find an explanation for why the codeforces community responded to the previous campaigns but not to the Tunisian campaign. Please share your thoughts!

Hi, I tried to change my handle to Bakry but it said: "this handle is currently in use"

but this handle didn't participate in any contest or post any comments and it's inactive from 2016.

Also, my friend tried to change his handle to Dr_Evil (which is inactive from 9 years) but he faced the same problem.

MikeMirzayanov

hello, there's something weird happened to me in szkopul website which caused TLE and after small changes to the code, it got AC..it happened to me in 2 problems.

1 — first problem : POI10-sums

I got 90 with this code and got TLE in test case 8 , but after that I got the full score using this code , the only difference between the two codes is that loop in dijkstra which in first code is :

for(int i = 0 ; i < n ; ++i)
{
    int now2 = now + arr[i] ;
    int cur2 = (cur + arr[i]) % arr[0] ;
    if(now2 > 1e9)
        continue ;
    if(now2 < vis[cur2] && now2 <= 1e9)
    {
        vis[cur2] = now2 ;
        q.push({now2 , cur2}) ;
    }
}

but in second code it's :

for(int i = 0 ; i < n ; ++i)
{
    int now2 = now + arr[i] ;
    int cur2 = (cur + arr[i]) % arr[0] ;
    //if(now2 > 1e9)
    //    continue ;
    if(now2 < vis[cur2] && now2 <= 1e9)
    {
        vis[cur2] = now2 ;
        q.push({now2 , cur2}) ;
    }
}

so the only difference is that I put this comment , there's no additional loop or nothing and the condition also was right.

2 — second problem : POI15-seals

I got 56 with this code and got TLE at test case 6, 7, 8, and 9, after that I made a small change and got 100 with this code, the only difference is that I made

char arr[n][m] , arr2[a][b] ;

in the first code , and replaced it with

vector<string>arr(n) ;
vector<string>arr2(a);

in the second code, and I don't think that makes that great difference because it's the same time in taking input.

so I would like to know what makes first codes in this two problems get TLE and after very small differences it got the full score even that these small differences don't affect the time of the codes.

hope the blog wasn't long and hope to know the reason of TLE.

Thanks.

after rating updated in Codeforces....now ratings returned as it was before the last contest...even in contest standing there's no rating changes....so what's the reason for that

UPD : ratings came back

When I opened problem set and sorted it , It showed me palindromic twist is the first!!

Update : It's solved now

IOI 2018 day 2 live streaming

IOI 2018 live ranking

Why Wrong Answer in this Problem

I Solved it using Segment tree and lazy propagation

Problem Link : http://www.spoj.com/problems/CDC12_H/

My Solution Link : https://ideone.com/Td4sDM

Hello CF Community

From 20 minutes Facebook announced Facebook Hacker Cup 2018.

Link of Post : https://www.facebook.com/hackercup/posts/1915605128471666

They Said That To Compete You must be higher than 18 years

So Is there way to participate in Facebook Hacker Cup For People < 18 ?

At Most For Competing Not For Winning Prizes

I Found This Library on GitHub which is For preparing Tests For Problems and It's written in C++ , I Think It will help Problem Setters For Rounds

https://github.com/ifsmirnov/jngen

Anyone have good resources for tabulation in DP

Hello ,

I saw most of programmers in Codeforces use Tabulation more than Memoization So , Why most of competitive programmers use Tabulation instead of memoization ?

It's the first problem for me to solve with DFS , So I can't understand why it's wrong Answer on test 6 The link of code and submission : http://codeforces.com/contest/580/submission/30840380 Problem link : http://codeforces.com/problemset/problem/580/C

Is there's anyone has good tutorial or Video that describe Bitmask with cases ? In C++

There's Wrong Answer on test case 14 I tried to solve it But What's in Code wrong that lead to print 146 instead of 120 Code : https://ideone.com/gwUN8C Problem : http://codeforces.com/contest/186/problem/B Submission : http://codeforces.com/contest/186/submission/30480217

I want to Know what's the answer for this Problem And What's the technique to solve with ? http://codeforces.com/contest/842/problem/A

I have Problem now in Codeforces when I submit solution for Problem it give me in queue I waited +13 minutes but it's also in queue Any Solution for this Problem ?

What's the needed Math for problem Solving What's necessary To learn in Mathematics in Algebra