Hello everyone!

We are back with another Premier round!

Repovive Premier Round 4 will be held next Sunday.

Premier rounds are currently the highest level among our contest series. We hope you enjoy it!

• Start Time: Sunday, 24 May 2026, 14:35 (UTC)
• Duration: $$$2$$$ hours, $$$30$$$ minutes
• Registration: https://repovive.com/contests/9

The contest is rated for everyone.

• Writers: ender_shayan, mohammadsam, Ali_BBN, AmirAli-Asgari, Hamed_Ghaffari, Bahamin and AmShZ
• Testers: Amoo_Safar and _R00T.

See you on the leaderboard!

UPD1: Congratulations to the top participants:

• 1: 244mhq
• 2: Um_nik
• 3: Ormlis
• 4: potato167
• 5: ainta
• 6: turmax
• 7: DanielChang
• 8: Golovanov399

Hello everyone!

The next Standard round is here.

Repovive Standard Round 3 will be held next Sunday.

• Start Time: Sunday, 17 May 2026, 14:35 (UTC)
• Duration: $$$2$$$ hours
• Registration: https://repovive.com/contests/8

The contest is rated for everyone.

• Writers: GreatShinobiOwl, AmShZ, Hamed_Ghaffari, AmirAli-Asgari, _R00T and mohammadsam
• Tester: Amoo_Safar and Bahamin

See you on the leaderboard!

UPD1: Fortunately, the contest went smoothly without any issues. You can view the solutions in the Learn tab.

Congratulations to the top participants:

• 1: alexwice
• 2: Golovanov399
• 3: Ormlis
• 4: Kareem_Elgoker
• 5: Dindin
• 6: wuhudsm
• 7: DanielChang
• 8: Mohammad Sajjad Akhavan Behabadi
• 9: Xellos
• 10: MarioYC

Hello everyone!

The first Starter round is here!

Starter rounds are designed to be beginner-friendly, with a level close to Codeforces Div.3 / AtCoder ABC. Since our rating system is still taking shape, this contest will be rated for everyone.

• Start Time: Sunday, 10 May 2026, 14:35 (UTC)
• Duration: $$$2$$$ hours
• Registration: https://repovive.com/contests/7

The contest is rated for everyone.

• Writer: AmShZ
• Tester: Hamed_Ghaffari

See you on the leaderboard!

Hello everyone!

We are very happy that our previous contest was held without issues.

The next Premier round is here.

Premier rounds are currently the highest level among our contest series. We hope you enjoy it!

• Start Time: Sunday, 3 May 2026, 14:35 (UTC)
• Duration: $$$2$$$ hours, $$$30$$$ minutes
• Registration: https://repovive.com/contests/6

The contest is rated for everyone.

• Writers: AmShZ, Hamed_Ghaffari and AmirAli-Asgari
• Testers: Amoo_Safar, Ali_BBN and Shayan

See you on the leaderboard!

UPD1: Fortunately, the contest went smoothly without any issues. You can view the solutions in the Learn tab.

Congratulations to the top participants:

• 1: 244mhq
• 2: Um_nik
• 3: HIR180
• 4: potato167
• 5: jiangxinyang
• 6: hitonanode
• 7: Rubikun
• 8: Golovanov399
• 9: DanielChang
• 10: MarcosK

I and Amoo_Safar always discuss our lazy segment tree logic.

The difference is this:

When I enter a node, I first apply its pending lazy value to the node itself.

But Amoo_Safar's assumption is that when he enters a node, the lazy value has already been applied before.

Below I show how this difference appears in implementation.

Amoo_Safar's style

In this style, the node is considered already updated correctly. The lazy value only means that this effect still has to be pushed to the children later.

So before going deeper, we call shift(id).

void upd(int id, int val) {
    seg[id] += val;
    lazy[id] += val;
}

void shift(int id) {
    if (!lazy[id]) return;
    upd(id << 1, lazy[id]);
    upd(id << 1 | 1, lazy[id]);
    lazy[id] = 0;
}

void update(int id, int l, int r, int ql, int qr, int val) {
    if (qr <= l || r <= ql) return;
    if (ql <= l && r <= qr) {
        upd(id, val);
        return;
    }
    shift(id);
    int mid = (l + r) >> 1;
    update(id << 1, l, mid, ql, qr, val);
    update(id << 1 | 1, mid, r, ql, qr, val);
    seg[id] = pull(seg[id << 1], seg[id << 1 | 1]);
}

My style

In this style, when I enter a node, I do not assume its pending lazy has already been applied to the node itself.

So the first step is to call shift(id, l, r) and make the node clean at that moment.

void shift(int id, int l, int r) {
    if (!lazy[id]) return;
    seg[id] += lazy[id];
    if (r - l > 1) {
        lazy[id << 1] += lazy[id];
        lazy[id << 1 | 1] += lazy[id];
    }
    lazy[id] = 0;
}

void update(int id, int l, int r, int ql, int qr, int val) {
    shift(id, l, r);
    if (qr <= l || r <= ql) return;
    if (ql <= l && r <= qr) {
        lazy[id] += val;
        shift(id, l, r);
        return;
    }
    int mid = (l + r) >> 1;
    update(id << 1, l, mid, ql, qr, val);
    update(id << 1 | 1, mid, r, ql, qr, val);
    seg[id] = pull(seg[id << 1], seg[id << 1 | 1]);
}

Both are correct. The main difference is just the invariant you keep in your head while writing the code.

Which one do you use, and why?

Hello everyone!

We are back!

Due to the ongoing war in Iran, we had to postpone Repovive Standard Round 2.
While the situation prevented us from hosting the contest on time, we used this period to fix several technical issues and improve the platform.

We are now ready to host Repovive Standard Round 2. We hope you enjoy it!

• Start Time: Sunday, 19 April 2026, 13:35 (UTC) (Note the unusual starting time)
• Duration: 2 hours
• Registration: https://repovive.com/contests/5

The contest is rated for everyone.

• Writers: AmShZ and Hamed_Ghaffari
• Testers: Amoo_Safar, Ali_BBN and Shayan

See you on the leaderboard!

UPD1: Fortunately, the contest went smoothly without any issues. You can view the solutions in the Learn tab.

Congratulations to the top participants:

• 1: jeroenodb
• 2: HIR180
• 3: zaahir
• 4: RockyYue
• 5: 300iq
• 6: turneja
• 7: amirhoseinfar1385
• 8: anirudhc69
• 9: Мурадис
• 10: Golovanov399

Hi everyone,

I’ve been wondering about a question that might be quite useful for contest platform organizers. If a contest is held on a Sunday, what starting time do you prefer the most?

If you had to choose between these options:

• 10:00 UTC
• 12:00 UTC (Usual AtCoder time)
• 14:30 UTC (Usual Codeforces time)
• 16:00 UTC

Or if you prefer a completely different time, please let me know the time as well as your time zone.

We’re excited to announce our upcoming contest, Repovive Standard Round 1!

• Start Time: Wednesday, 25 February 2026, 14:35 (UTC) Sunday, 1 March 2026, 14:35 (UTC) Monday, 2 March 2026, 14:35 (UTC).

• Duration: $$$2$$$ hours.

• Registration: https://repovive.com/contests/8.

UPD: Due to a schedule conflict with a Codeforces contest, the start time has been changed.

UPD2: The contest has been postponed by one more day.

The contest is rated for everyone.

• Our Writers: Hamed_Ghaffari, _R00T, Bahamin, AmirAli-Asgari and me.

• Our Testers: Amoo_Safar, mohammadsam, Ali_BBN, Hmzaawy and Shayan.

The Innovation Game (TIG) is sponsoring this contest!

To make this contest even more exciting, TIG is dropping some rewards:

• 1st Place: $100 in TIG tokens
• 2nd Place: $50 in TIG tokens
• 3 random participants from the Top 100 will each receive $20 in TIG tokens
• 3 random participants will each receive $20 in TIG tokens

When you finish competing, check out what TIG is building. They run a continuous, 24/7 algorithmic competition to ensure frontier algorithms remain open-source. You can submit optimized code to win from their weekly prize pools (currently $9K in TIG Tokens). Learn more and start earning on their network here.

We’re excited to announce our upcoming contest, Repovive Premier Round 2!

• Start Time: Monday, 16 February 2026, 14:35 (UTC).

• Duration: $$$3$$$ hours.

• Registration: https://repovive.com/contests/7.

The contest is rated.

• Our Writers: Hamed_Ghaffari, _R00T, Ali_BBN, Ehsan Heidari and me.

• Our Testers: Amoo_Safar, AmirAli-Asgari, mohammadsam, Bahamin and Hmzaawy.

We’re looking forward to seeing you in the contest!

We’re excited to announce our upcoming contest, Repovive Premier Round 1!

We apologize for the judge issues that occurred in our previous contest, and we truly hope everything runs smoothly this time. Regarding the contest being rated, we decided to keep it rated despite the recent problems, since making it unrated would also come with its own negative consequences. Also, the Hello 2026 Round was cancelled because the internet was cut nationwide in Iran by the government, and our problem-setters were Iranian. We’re very sorry for the inconvenience and hope you can understand our difficult situation. Finally, we want to sincerely thank everyone who continues to support us.

• Start Time: Sunday, 8 February 2026, 14:35 (UTC).

• Duration: $$$3$$$ hours.

• Registration: https://repovive.com/contests.

More details about our contest series and what the Premier Rounds are can be found in this blog.

We will also have the full solution discussion with Um_nik on Repovive TV.

• Our Writers: Atalasion, AmirAli-Asgari, Hamed_Ghaffari, _R00T, Shayan and me (AmShZ).

• Our Testers: Amoo_Safar, mohammadsam, Keshi and Hmzaawy.

Good luck, and we’re looking forward to seeing you in the contest!

We’re excited to announce our upcoming contest, Repovive Hello 2026 Round!

• Start Time: Sunday, 11 January 2026, 14:35 (UTC).
• Duration: $$$3$$$ hours.
• Registration: https://repovive.com/contests.

The contest is rated.

• Our Writers: _R00T, Hamed_Ghaffari, AmirAli-Asgari, Shayan and me (AmShZ).

• Our Testers: Amoo_Safar, mohammadsam and Hmzaawy.

We’re looking forward to your participation! Happy new year!

Update: We have to postpone our contest to the next Sunday. There is an internet blackout outgoing in Iran, and since most of our authors reside in Iran, we could not hear back from them till now.

We’re super excited to announce our upcoming contest, Repovive Goodbye 2025 Round!

• Start Time: Sunday, 28 December 2025, 15:35 (UTC).
• Duration: $$$3$$$ hours.
• Registration: https://repovive.com/contests.

The contest is rated. You can also check out the problems from Repovive Opening Round, here: https://repovive.com/contests/4.

• Our Writers: Amoo_Safar, _R00T, Ali_BBN, mohammadsam, Shayan and me (AmShZ).

• Our Testers: Hamed_Ghaffari, alireza_kaviani, ParsaDox, AmirAli-Asgari, Hmzaawy, AKprinceofpersia and Akhb.

If you’d like to become a tester and help us hold future contests, please let us know in the comments.

Prizes (total: $500 USD):

• 1st place: $200
• 2nd place: $100
• 3rd place: $50
• 3 random participants from the top 100: $25 each
• 3 random participants from all contestants: $25 each

All participants with at least one submission: 100 veltos

Veltos can turn into many things, including t-shirts, mugs, and saving your streaks.

The prize winners of Repovive Goodbye 2025 Round:

• 1: Um_nik — $200
• 2: dXqwq — $100
• 3: Golovanov399 — $50

• 10: Isaac Chan — $25

• 59: Null — $25
• 98: Prateek Verma — $25
• 159: Ilya Ghadiri Anari — $25
• 197: Shuvo Morsalin — $25
• 223: Dharun Kaarthick S — $25

If you are a winner, we will reach out to you by email.

We’re looking forward to your participation! Merry Christmas!

Hey everyone,

We are organizing Repovive Testing Round #2. This is the second of three testing rounds that will take place before our Opening Round.

All problems are original and authored by us. While we have reserved some of our best problems for the Opening Round, we hope you will enjoy this set as well.

Start time: December 10th at 14:35 UTC.

Registration: https://repovive.com/contests.

We would also appreciate any feedback on the problems and the platform after the round.

Hi Codeforces!

Keshi, alireza_kaviani and I are delighted to invite you to participate in Codeforces Round 800 (Div. 1) and Codeforces Round 800 (Div. 2).

• Start time: Jun/16/2022 17:35 (Moscow time)
• Duration: $$$120$$$ minutes
• Number of Tasks: $$$6$$$ for both divisions
• Rated range: ($$$-\infty$$$,$$$1899$$$] for Div2, [$$$1900$$$, $$$\infty$$$) for Div1

We are honored to have set the 800th Codeforces round. We wish this wonderful platform all the best along with many other exciting rounds.

Huge thanks to the following people:

• antontrygubO_o for his breath-taking coordination.

• Our testers Um_nik, errorgorn, Koosha_Mv, irkstepanov, ymmparsa, sohsoh, fatemetmhr, Dorost, nor, pooya-shams, Arnch, Kahou and mosaev for testing the round and providing invaluable feedback.

• radiohead because we got inspiration from them while coming up with task names.

• MikeMirzayanov for the amazing platforms Codeforces and Polygon!

• Last but not least, to all the participants of this round!

Thanks to NEAR for supporting this round, details can be found in this post.

We have worked hard to keep the statements clean and the pretests strong!

Please read all of the problems and their notes, enjoy your time and solve as many as you can! Good luck have fun to everyone!

The scoring distributions will be announced later.

UPD: Here are the scoring distributions:

• Div. 1: 750 1000 1500 2250 2500 3000

• Div. 2: 500 1000 1500 1750 2250 3000

UPD: Editorial is out!

Hi Codeforces!

Dio, Keshi, Tet, alireza_kaviani, Davoth, AliShahali1382 and I are delighted to invite you to participate in Codeforces Round 722 (Div. 1) and Codeforces Round 722 (Div. 2), which will be held at May/24/2021 17:35 (Moscow time). Each division will have 6 problems and 2 hours and 15 minutes to solve them.

The curse has finally been lifted! We are proud to announce that antontrygubO_o didn't reject even a single task from the Div. 1 part!

Huge thanks to the following people:

• antontrygubO_o for being an outstanding coordinator; This round wouldn't have happened if it weren't for him.

• Our ever-growing army of testers gamegame, Amoo_Safar, Atreus, dorijanlendvaj, aarr, Monogon, EnEm, N.N_2004, AaParsa, _Seyed37_, Roham, Clix, Narut, SinaSahabi, sinamhdv, arvindr9, shokouf, munghatekartik, Ali_Tavakoli, vodacbaoan, Shahraaz, -Suto-, coderz189, kassutta, the_borono, saarang, iANikzad, Etherite and -this-is-obd- for testing the round and providing invaluable feedback.

• MikeMirzayanov for the amazing platforms Codeforces and Polygon!

• Last but not least, to all the participants of this round!

For the sake of having short statements, this round does not have a theme. The characters featured in the statements are: Soroush (Tet), Sifid (Davoth), Parsa (Dio), Nima (N.N_2004), AaParsa (AaParsa), Haj Davood (davooddkareshki), Kavi (alireza_kaviani), Keshi (Keshi), Mashtali (AliShahali1382) and AmShZ (AmShZ).

Please read all of the problems and their notes, enjoy your time and solve as many as you can! Good luck have fun to everyone!

The scoring distributions will be announced later.

UPD: Here are the scoring distributions:

• Div. 1: 750 1000 1750 2000 2750 3000

• Div. 2: 500 1250 1750 2000 2750 3000

UPD: Editorial is out!

l" Nowruz ", The Ancient Persian New year and the harmony of new birth of the nature,

has been celebrated for over 3000 years!

Happy new year 1400 to Iranians of all relligious and cultures and all other nations : )

(This will be also our last year of the 14th's century!)

ز کوی یار می آید نسیم باد نوروزی

ازین باد ار مدد خواهی چراغ دل برافروزی

Translation :

The fragrant breeze of the nowruz came from a friend

if desire aid from this breeze, you will kindle the lamp of your heart.

" The Iranian poet, Hafez Shirazi "

Hi everyone!

I'm writing this blog to give some "constructive" feedback on the current state of the tasks in the recent CF rounds. Personally speaking, I believe that tasks are becoming more and more theoretical contest after contest (by theoretical I mean tasks that are not challenging to code).

Nowadays we rarely see tasks that require algorithmic thinking or coding skills.

I personally blame this on the procedure of proposing contests, it's natural for setters to start with proposing tasks that require some coding and later on replace them with theoretical tasks (which are easier to come up with) after their first set of tasks gets rejected by the coordinators.

In fact, some setters might presume that the vast number of theoretical tasks means that they are more probable to get accepted by the coordinators.

The point I'm trying to make is that WE are the ones who are creating these tasks, therefore WE are responsible for creating this mess. Hence, I humbly request the setters to try and come up with tasks that have a rather challenging code.

Hi

First of all congrats too Codeforces community for having more than 23000 participants in an official round

If I want to be honest I'm not really okay with Codeforces right now, cause recently its servers went down a lot and even in the contests there's a queue that is really annoying, I have no idea about Codeforces problems or why they don't fix these issues but, as a participant I wanted to ask Mike Mirzayanov to solve these issues (like the one that was solved before about the queues and system test speed, thnx btw ). Cause with COVID 19 out there, I spend most of my time in Codeforces right now, I am sure that there are others that are like me.

And last but not least just wanted to end this blog by some beautiful quotes:

*Dab when you cough *Dab when you sneeze *Dab to beat coronavirus

-Paul Pogba 2020

The last contest's Codeforces Round 590 (Div. 3) was very slow; every submit, was in queuing about 10 minutes. I've lost a lot of time.

Please fix these problems :)

What's your favorite problem or contest?

Please Comment it ;)