tourist's blog

By tourist, history, 7 weeks ago, translation, In English,

Here is the tutorial of VK Cup 2017 Round 3 and Codeforces Round #412. Enjoy!

Is it rated?
T-Shirt Hunt
Success Rate
Dynamic Problem Scoring
Prairie Partition
Perishable Roads
Blog Post Rating
Test Data Generation

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By tourist, 2 months ago, translation, In English,

Hi everyone!

The last elimination round of VK Cup 2017, Round 3, will take place on May 7 at 18:35 MSK (check your timezone here), along with separate Codeforces Round #412 for both divisions. All three rounds will be three hours long, and all three rounds will be rated.

The contest "VK Cup 2017 — Round 3" is for teams qualified from Round 2 or Wildcard Round 2. The top 20 teams will advance to the final which will be held in July 2017 in Saint Petersburg!

Huge thanks to KAN, qwerty787788, PavelKunyavskiy, AlexFetisov, MikeMirzayanov, and VK company for making this round possible.

Codeforces will be the main character of most problems. Don't forget that it's useful to read the statements of all the problems.

Good luck!

As we're in year 2017, the scoring will obviously be static. The exact scoring distribution will be announced before the round.

UPD 1. The scoring distribution is:

Div. 1 and VK Cup Round 3: 500 — 1000 — 1750 — 2500 — 2750 — 3500

Div. 2: 500 — 1000 — 1500 — 2000 — 2750 — 3500

UPD 2. Due to yesterday's registration troubles the start of the contest is delayed by 10 minutes.

UPD 3. Congratulations to the winners!

VK Cup Round 3:

  1. zemen, Zlobober
  2. V--o_o--V, LHiC
  3. RomaWhite, witua
  4. YakutovDmitry, BudAlNik
  5. Golovanov399, I_hate_ACM

Div. 1:

  1. Petr
  2. yosupo
  3. rng_58
  4. uwi
  5. Nezzar

Div. 2:

  1. ltaravilse
  2. btk15049
  3. RCG
  4. SUSTechDFS
  5. hieutrungle

UPD 4. Tutorial is now available.

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By tourist, history, 5 months ago, translation, In English,

XVII Open Cup Stage 10: Grand Prix of Gomel takes place on Sunday, February 5, 2017, at 11:00 AM Petrozavodsk time.

The link to the contest. You need an Open Cup login to participate.

I'm the writer of all the problems.

This problemset will also be used at Barcelona ACM ICPC Bootcamp on Monday, February 6. Unfortunately, this means I have to ask you to refrain from discussing the problems in public until the end of the contest in Barcelona on Monday, 5:30 PM Barcelona time.

Let's discuss the problems here on Monday evening!

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By tourist, history, 7 months ago, translation, In English,

Topcoder Open 2016 Algorithm Final Round starts in 28 minutes.

The finalists are bmerry, Enot (aka enot.1.10), Kankuro (aka vepifanov), krijgertje, Petr and rng_58.

Live broadcast will be available on Twitch.

Watch the action in the Topcoder Arena.

Also follow my live commentary on Twitter.

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By tourist, 5 years ago, translation, In English,

Hello everyone!

As many of you already know, today is the day for Codeforces Round #127 missing which is really undesirable ;)

Original problems for you were created by tourist and Romka. We tried to emphasize the ideological component of the problems, thus we hope that you'll spend more time thinking than coding. Special thanks for helping in setting the contest go to Codeforces coordinator Gerald. We also thank Delinur for translating the problem statements and Alex_KPR for reviewing them.

We hope that this round won't be just a regular Codeforces round for you, but will bring you new experience and new knowledge. For the authors all problems are equally easy, yet we tried to arrange them in decreasing order of simplicity :)

Problems' point values in Division 1 are 1000-1000-1500-2000-2500. Problems' point values in Division 2 are 500-1000-2000-2000-2500.

Wish you success!

UPD: The contest is over, thanks all for participating. We hope you enjoyed it :)

In Division 1 rng_58 was a clear winner, solving all 5 problems in an hour and a half! No one else managed to solve all problems in two hours.

The winners in Division 1 are (full results):

  1. rng_58

  2. peter50216

  3. liympanda

  4. White_Bear

  5. havaliza

In Division 2 every problem was solved by somebody, but nobody managed to solve all problems. The battle was very tough and the gaps were very small.

The winners in Division 2 are (full results):

  1. Leewings

  2. snow_lotus

  3. 72VanVector_SevNTU

Congratulations to the winners!

UPD2: The editorial is available now.

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By tourist, 6 years ago, translation, In English,
Hello everyone!

I invite you to participate in the upcoming short contest at ( The contest starts on November 20 at 20:00 Moscow time (check the starting time in other time zones here). This time I'm setting the problems, while Anton Lunyov (A_A_Lunyov) is the tester. Anton made a significant contribution into setting the contest, so my big "thank you" goes to him :)

Here is some information for those who has never participated in short contests at CodeChef. The length of the contest is 2.5 hours, there will be 5 problems of different difficulty levels. The contest will be held by the traditional ACM rules. No special registration for the contest is needed, it's enough to register at the CodeChef site.

Unfortunately I won't be able to monitor the contest as I'll participate in All-Russian School Team Olympiad in Programming on the same day. Nevertheless, Anton will be able to answer all your questions (if any).

Good luck! ;)

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By tourist, 7 years ago, translation, In English,
Contest discussion

Problem A. Noldbach problem

To solve this problem you were to find prime numbers in range [2..N]. The constraints were pretty small, so you could do that in any way - using the Sieve of Eratosthenes or simply looping over all possible divisors of a number.
Take every pair of neighboring prime numbers and check if their sum increased by 1 is a prime number too. Count the number of these pairs, compare it to K and output the result.

Problem B. Hierarchy

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