Lewin's blog

By Lewin, history, 6 months ago, In English,

Here's the tutorial. Code can be found in this link (more will be added there soon): https://www.dropbox.com/sh/xwxn3zrl1icp3i2/AACtYSdYH0KlTEdVgCFFgPrYa?dl=0

Zoning Restrictions Again
Double Matrix
Hide and Seek
Chladni Figure
Thanos Nim
Palindrome XOR
Rainbow Coins
Zigzag Game

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By Lewin, 6 months ago, In English,

Hello again Codeforces!

The Forethought Future Cup Final round will start on May 4th, 10:05am PDT. This round will be rated for everyone. There will be three separate rounds, one for onsite contestants, one for div1, and one for div2. Onsite and div1 will have the same problems. Each round will have 6 problems and be 2 hours long.

Here is a table of the onsite contestants.

scott_wu neal ACRush Fdg Ra16bit
Kenny_HORROR liymbear ll931110 xiaowuc1 Suzukaze
yzyz stevenkplus pmnox OpalDshawn NEU20133823
tap_tapii Svlad_Cjelli Emiso davidberard gojira
dinosaurs batyrkhan14 robot-dreams kfqg

The onsite round has cash prizes:

  • 1st: $500
  • 2nd: $250
  • 3rd: $100
  • 4th — 10th: $50

Thanks to ismagilov.code, mohammedehab2002, Jeel_Vaishnav, Learner99, 300iq, dojiboy9, fortune, y0105w49, KAN, arsijo for testing and coordination. Also, thanks to cyand1317 for one of the problems. Of course, thanks to MikeMirzayanov for Codeforces and Polygon, and for allowing us to host the round.

There might be some interactive problems again, so please read the interactive problem guide if you haven't before.

If you're still interested in applying, please fill out the form.

Updates

UPD 1 The scoring distribution will be:

  • Div2: 500-1000-1500-2000-2500-3000
  • Div1: 500-1000-1500-2000-2500-3250

UPD 2 Pictures from the onsite round: https://codeforces.com/blog/entry/66876

UPD 3: I'm sorry, but to prevent the leak of onsite results, we will postpone the start of system testing a bit. As soon as the closing ceremony finish at Forethought office, we will immediately start the system testing of the rounds. Until this time, the rounds will be hidden. But don't panic, this will only be temporary and we will return everything soon.

UPD 4: The results will be in around 90 minutes after the end of the competition.

UPD 5: Tutorial: https://codeforces.com/blog/entry/66878

UPD 6: Congratulations to the winners:

Onsite contest:

1 scott_wu
2 ACRush
3 neal
4 xiaowuc1
5 Svlad_Cjelli
6 Ra16bit
7 ll931110
8 stevenkplus
9 yzyz
10 pmnox

Div 1 contest:

1 Benq
2 Petr
3 Errichto
4 aid
5 Endagorion

Div 2 contest:

1 Ezys
2 nitishk24
3 gonP
4 trabbbart
5 Randl

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By Lewin, history, 6 months ago, In English,

I wrote a post about coming up with problem ideas here with some examples: https://www.topcoder.com/blog/how-to-come-up-with-problem-ideas/

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By Lewin, history, 6 months ago, In English,

Here's the tutorial. Code can be found in this link: https://www.dropbox.com/sh/wfr12qqhcrdwwlv/AAAgg-7NcqRHIysVjHvmcR_Ta?dl=0

Love A
Hate A
Tree Diameter
Frog Jumping
Hot is Cold
Leaf Partition
Zoning Restrictions
Satanic Panic

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By Lewin, 6 months ago, In English,

Hi Codeforces!

I'm excited to announce the Forethought Future Cup! It will consist of two rounds, an online round on April 20th, 11:05am PDT, and an onsite round on May 4th, 10:05am PDT. Both of these rounds will be rated and open for all participants. The top 25 local contestants near San Francisco will be invited to the Forethought office to take part onsite.

Each round will be a combined round. In the first round, there will be 8 problems in 2.5 hours. There will be at least one interactive problem in this round. Please read the interactive problem guide if you haven’t already.

The problems in this round were all written by me. Thanks to ismagilov.code, mohammedehab2002, Jeel_Vaishnav, Learner99, dojiboy9, fortune, y0105w49, KAN, arsijo for testing and coordination. Of course, thanks to MikeMirzayanov for Codeforces and Polygon, and for allowing us to host the round.

Prizes

T-shirts will be awarded to all onsite participants. 25 shirts will also be randomly awarded to contestants in the elimination round with ranks 1 to 250. The onsite round will also have some monetary prizes:

  • First: $500
  • Second: $250
  • Third: $100
  • 4th — 10th: $50

About Forethought:

At Forethought, our mission is to use AI technology to augment human abilities and make everyone “a genius at their job”. Our main product is Agatha, an assistant that helps customer support agents answer cases more quickly and confidently by suggesting answers and triaging cases. We've raised over $10M in VC funding and were the winners of 2018 SF TechCrunch Disrupt Battlefield.

I joined Forethought back in December 2018. We are a small 12 person startup, and have a lot of competitive programmers on our team, including me, y0105w49, fortune, and dojiboy9 (our CEO, who is also an ICPC World Finals Judge). I’m happy to answer any questions about working here in the comments below or through PM.

We’re hiring! Please fill out this form if you are interested.

Updates

UPD 1 The scoring distribution will be 500-1000-1500-2250-2500-3250-3250-3750

UPD 2 Tutorial can be found here: https://codeforces.com/blog/entry/66639

UPD 3 Congratulations to the top 5!

  1. tourist
  2. Benq
  3. Radewoosh
  4. yutaka1999
  5. ainta

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By Lewin, 8 months ago, In English,

NAIPC is happening again on March 2nd (start time). Information about the contest can be found on this page. Information about registering can be found on here. You can register in teams of up to 3. The deadline for registration is February 28th. This contest will be hosted on Kattis again.

A few hours later, it will be available as an open cup round as the Grand Prix of America (start time). Please participate in only one of them, and don't discuss problems here until after the open cup round has ended.

You can see some past years' problems here: 2018, 2017

UPD 1: Registration is ending soon.

UPD 2: Please don't discuss until after open cup is over.

UPD 3: You can find test data and solutions here: http://serjudging.vanb.org/?p=1349

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By Lewin, history, 11 months ago, In English,

I recently added the div 1 regional to the gym here. You can virtual participate at any time.

Solutions are available on the contest website if you want to look at them up afterwards here (soon...). Feel free to discuss problems afterwards.

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By Lewin, history, 12 months ago, In English,

Recently, I wrote about my experiences with problem writing. This was something I haven't really talked about, and I felt it was time to share.

Read here: https://www.topcoder.com/blog/a-problem-writing-journey/

Feel free to leave comments or questions!

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By Lewin, history, 19 months ago, In English,

I'm not sure I've seen a post about this yet. Topcoder has posted their schedule for online rounds for TCO here: http://tco18.topcoder.com/algorithm/schedule/

It seems the round structure also seems to have changed. The rounds are 1A,1B, 2A,2B, 3A,3B, and a single round 4. Round 4 feeds directly into the onsite, with 14 finalists (and also 2 from a wildcard round, for a total of 16, 4 more from last year).

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By Lewin, history, 19 months ago, In English,

NAIPC is coming up on March 24th (start time here). More information about the contest can be found on this page. More information on how to register can be found on this page. You can register in teams of up to 3. This contest will be on Kattis.

Several hours later, it will be available as an open cup round as the Grand Prix of America (start time here). Please only participate in one of them, and don't discuss problems here until after the open cup round has ended.

The deadline to register for the contest on Kattis is March 21st. You will need an ICPC account to register (you can see instructions in the link above on how to create one if needed).

You can see some past years' problems here: 2017, 2016

UPD 1: The deadline to register your team is soon.

UPD 2: Contests are over

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By Lewin, history, 20 months ago, In English,
Police Patrol
Alphabetic Subsequence
Infinite Graph Game
Stamp Stamp Stamp
Increasing Sequence
Yet Another Binary Matrix

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By Lewin, history, 20 months ago, In English,

Hello everybody!

On Mar 3, 10:00 Moscow time, Round 1 of Yandex.Algorithm 2018 competition will take place. I wrote the majority of the problems in this contest, with some additional help from GlebsHP.

I would like to thank GlebsHP for all his help with coordinating this round, MikeMirzayanov for polygon, and of course, everyone who took the time to test this round.

See you in the competition soon!

Editorial here: http://codeforces.com/blog/entry/58135

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By Lewin, history, 20 months ago, In English,

Hi! Topcoder SRM 730 will happen soon.

Time: 7:00am EDT Tuesday, February 20, 2018

Calendar: https://www.topcoder.com/community/events/

I'm the writer of this round. Hope to see you all participate!

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By Lewin, 22 months ago, In English,

Here's the editorial. Hope you have a happy new year!

Code can be found here: https://www.dropbox.com/sh/i9cxj44tvv5pqvn/AACQs7LLNyTZT-Gt_AMf7UQFa?dl=0

New Year and Counting Cards
New Year and Buggy Bot
New Year and Curling
New Year and Arbitrary Arrangement
New Year and Entity Enumeration
New Year and Rainbow Roads
New Year and Original Order
New Year and Boolean Bridges

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Tutorial of Good Bye 2017
 
 
 
 
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By Lewin, history, 22 months ago, In English,

Hello everyone!

Another year has gone by. The last Codeforces contest of this year will be tomorrow, 29 Dec, 15:35 UTC.

The round details:

  • combined div1+div2
  • 8 problems
  • 2.5 hours
  • rated!!!

I'd like to thank the following people for helping with the round: KAN, winger, AlexFetisov, zemen, xiaowuc1, MikeMirzayanov. Without them, this round would not have been possible.

Scoring distribution will be posted later. Make sure to read ahead on the problems, since there may be some later problems that are easier for you. I hope to see you all at the contest, and good luck on the last chance to increase your rating this year!

EDIT1: The scoring distribution is 500-750-1000-1750-1750-2000-2750-3500

EDIT2: There will be a five minute delay for starting.

EDIT3: Editorial is here: http://codeforces.com/blog/entry/56713

EDIT4: Congratulations to the winners!

  1. Petr
  2. dotorya
  3. V--o_o--V
  4. Radewoosh
  5. Endagorion
  6. rng_58
  7. PavelKunyavskiy
  8. moejy0viiiiiv
  9. mmaxio
  10. Reyna

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By Lewin, history, 23 months ago, In English,

I recently added this regional to the gym here. You can virtual participate at any time.

Solutions are available on the contest website if you want to look at them up afterwards here. Feel free to discuss problems afterwards.

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By Lewin, history, 2 years ago, In English,

On Sunday, August 6th, 22:00 IST, we will hold the 2nd elimination for IndiaHacks (some more details here). The top 900 individuals who qualified through previous rounds will have the opportunity to participate in this round. The top 25 global participants and top 25 Indian participants will advance to the final round. The link to the contest is here.

After the official round is over, the next morning, on Monday, August 7th, 11:35 IST, we'll hold an unofficial unrated mirror here on Codeforces. This mirror will have ICPC rules. For participants of the official round, please hold off on discussing the problems publicly until after this mirror is over.

I was the author of the problems in this set, and I hope you will enjoy the problems. I would like to thank zemen for testing the set, Arpa for writing editorials, r3gz3n for his help on the HackerEarth side, KAN for helping us set up the mirror contest, and of course MikeMirzayanov for the great Polygon/Codeforces platform.

The round will consist of 6 problems and you will have 3 hours to complete them. Please note that the problems will be randomly arranged in both rounds, since I couldn't figure out how to sort them by difficulty. Be sure to read all the problems.

UPD1: Updated time of official round and posted link to contest.

UPD2: We should have updated the leaderboard to accept solutions that followed the first version of the first problem. We have also increased the number of finalists to 60 total (30 global + 30 indian) based on this new leaderboard.

UPD3: Here is the list of qualifiers. Congratulations to everyone.

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By Lewin, history, 2 years ago, In English,

Didn't notice a post from cgy4ever.

Topcoder SRM 718 will happen in ~4 hours.

Tim: 9:00pm EDT Wednesday, July 12, 2017

Calendar: https://www.topcoder.com/community/events/

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By Lewin, history, 2 years ago, In English,

Hello everyone!

I would like to invite you to participate in Hackerearth June Circuits 2017. It's a long contest that will start on June 16, 2017, 21:00 IST (check your timezone). The contest will run for 9 days.

The problemset consists of 7 traditional algorithmic tasks and 1 approximate problem. For traditional algorithmic tasks, you will receive points for every test case your solution passes — so you can get some points with partial solutions as well. For the approximation task, your score depends on the best solution in the contest so far. Check contest page for more details about in-contest schedule and rules.

I'm the tester of the problemset you'll have to work on — thanks to jtnydv25, saatwik27, harshil, zscoder, Arunnsit for preparing these tasks.

As usual, there will be some prizes for the top five competitors:

  1. $100 Amazon gift card + HE t-shirt.
  2. $75 Amazon gift card + HE t-shirt.
  3. $50 Amazon gift card + HE t-shirt.
  4. HE t-shirt.
  5. HE t-shirt.

Good luck to everyone, and I hope to see you at the contest :)

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By Lewin, 2 years ago, In English,
Fibonacci Frequency
Rainbow Road
Wildcard Words
Counter Complexity
Avoiding Adjacent
Token Tree

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By Lewin, history, 2 years ago, In English,

Hello everybody!

On May 27, 23:00 Moscow time, Round 2 of Yandex.Algorithm competition will take place. I wrote the majority of the problems in this contest, with some additional help from Zlobober.

I would like to thank Zlobober for all his help with coordinating this round, MikeMirzayanov for polygon, and of course, everyone who took the time to test this round.

Please note, the problems will be randomly arranged, so make sure you read everything during the round :)

If you are using Java, please submit using Java 7 x32.

See you in the competition soon!

UPD 1: Editorial here: http://codeforces.com/blog/entry/52223

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By Lewin, history, 3 years ago, In English,

Hello everyone!

I would like to invite you to participate in Hackerearth April Circuits 2017. It's a long contest that will start on April 21, 21:00 IST (check your timezone). Contest will run for 9 days.

The problemset consists of 7 traditional algorithmic tasks and 1 approximate problem. For traditional algorithmic tasks, you will receive points for every test case your solution passes — so you can get some points with partial solutions as well. For the approximation task, your score depends on the best solution in the contest so far. Check contest page for more details about in-contest schedule and rules.

I'm the tester of the problemset you'll have to work on — thanks to jtnydv25, saatwik27, pkacprzak, r3gz3n, trytolearn for preparing these tasks.

As usual, there will be some nice prizes for the top five competitors:

  1. $100 Amazon gift card + HE t-shirt.
  2. $75 Amazon gift card + HE t-shirt.
  3. $50 Amazon gift card + HE t-shirt.
  4. HE t-shirt.
  5. HE t-shirt.

Good luck to everyone, and I hope to see you at the contest :)

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By Lewin, history, 3 years ago, In English,
Viscious Keyboard
Valued Keys
Voltage Keepsake
Volatile Kite
Vulnerable Kerbals
Varying Kibibits
Verifying Kingdom

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Tutorial of VK Cup 2017 - Round 2
 
 
 
 
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By Lewin, 3 years ago, In English,

Hello!

The round 2 of VK Cup 2017 will take place on April 16 at 18:35 MSK (check your timezone here), along with separate div1 and div2 Codeforces Round #409. The contest "VK Cup 2017 — Round 2" is for teams qualified from round 1. The top 100 teams will advance to the Round 3, while other ones will have one more chance in the Wild Card Round 2 later this month. Those who don't participate in the VK Cup can take part in the Codeforces Round #409 individually (problems will be available in English too). All three rounds last 2 hours, and all are rated.

The round would not be possible without the following people (in no particular order): KAN, Errichto, winger, AlexFetisov, LiChenKoh, xiaowuc1, MikeMirzayanov. Additionally, I thank VK company for sponsoring this contest.

As usual, the scoring distribution will be announced later.

UPD 1: The scoring distribution is as follows:

div2: 500 — 1000 — 1500 — 2000 — 2750

div1 and official round: 500 — 1000 — 175022502250

UPD 2: The tutorial is available here: http://codeforces.com/blog/entry/51598

Congratulations for the winners

Official round:

  1. LHiC, V--o_o--V
  2. I_love_Tanya_Romanova, enot110
  3. netman, andrew.volchek
  4. aid, ershov.stanislav
  5. MrDindows, Rubanenko

div 1:

  1. SirShokoladina
  2. moejy0viiiiiv
  3. jcccccccccccccccccccccsb
  4. TakanashiRikka
  5. Um_nik

div 2:

  1. ngkan146
  2. AlwaysWrong
  3. fgvfgfg1
  4. DryukAlex
  5. DorMOUSENone

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Announcement of VK Cup 2017 - Round 2
 
 
 
 
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By Lewin, history, 3 years ago, In English,

NAIPC is coming up on April 15 (start time here). More information can be found on the site. The contest will be on Kattis on the 15th. About 15 hours later, it will be available as an open cup round as the Grand Prix of America. Please only participate in one of them, and don't discuss problems here until after the open cup round.

The deadline to register for the contest on Kattis is April 12th. You can register by following instructions on this site: http://naipc.uchicago.edu/2017/registration.html# You will need an ICPC account to register.

You can see previous NAIPC rounds here: 2015, 2016. 2016 is also available in the codeforces gym here: http://codeforces.com/gym/101002

UPD 1: The deadline to register is in a couple of days.

UPD 2: Both contests are now over

NAIPC standings: https://naipc17.kattis.com/standings

Open Cup standings: http://opentrains.snarknews.info/~ejudge/res/res10376

I'll update this one more time with solutions once they are up.

UPD 3: Test data is available here (solutions may show up later, but I'm not sure when): http://serjudging.vanb.org/?p=1050

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