Nickolas's blog

By Nickolas, 3 weeks ago, translation, In English,

Marathon Match 98 PrincessesAndMonsters started on February 14th and will run for a week.

Ten participants (top 5 and 5 random) will get t-shirts! I am the writer :-)

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By Nickolas, 6 weeks ago, translation, In English,

Marathon Match 97 PointsOnTheCircle started on January 24th and will run for a week. I am the writer :-)

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

909A - Generate Login

The most straightforward solution is to generate all possible logins (by trying all non-empty prefixes of first and last names and combining them) and find the alphabetically earliest of them.

To get a faster solution, several observations are required. First, in the alphabetically earliest login the prefix of the last name is always one letter long; whatever login is generated using two or more letter of the last name, can be shortened further by removing extra letter to get an alphabetically earlier login.

Second, the prefix of the first name should not contain any letter greater than or equal to the first letter of the last name, other than the first letter.

Thus, a better solution is: iterate over letter of the first name, starting with the second one.

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

Codeforces Round #455 for Div 2 competitors will be held on December 27 at 19:35 MSK. As usual, Div 1 competitors can join out of competition.

The round will be rated.

This round is based on tasks for summer contest for interns algO(1). If you have seen the problems from that contest before, please don't participate in the round. The problems were prepared by Maxim Kalinin (slycelote), Alexander Milanin (Milanin), Ibragim Ismailov (ibra) and me (Nickolas).

The competitors will be given six problems and two hours to solve them. The scoring distribution will be 500-1000-1500-1750-2000-2500.

We hope you'll like the problems. Good luck!

UPD: thanks to HellKitsune, gritukan, gainullin.ildar, Arpa and Livace for testing the problems!

UPD: The contest is over. Editorial can be found here.

Congratulations to winners!

Div. 2:

  1. yzx_H2O
  2. skuecrk
  3. Vergara
  4. kadalbonek
  5. UoA_Nirvana

Div. 1:

  1. Benq
  2. dotorya
  3. uwi
  4. I_love_Tanya_Romanova
  5. ksun48

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By Nickolas, 3 months ago, In English,

Today the last fun Marathon of 2017 GarlandOfLights started. It will run for one week. I am the writer; enjoy :-)

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By Nickolas, 5 months ago, translation, In English,

Marathon Match 95 CirclesMix started on October 4th and will run for one week. You can find it in the list of active contests. I am the writer :-)

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By Nickolas, 7 months ago, In English,

Several Marathon matches were added to Topcoder event calendar:

  • Marathon Match 94, starting on August 16th — 1 week long.
  • lightning round leading to Warsaw regional event, runs August 29th — September 1st, open for everybody and awards TCO points.
  • Marathon Match 95, starting on October 4th — 1 week long.

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By Nickolas, 8 months ago, translation, In English,

The third round of TCO17 Marathon Competition PoisonedWine started yesterday. It will run for two weeks, and top 30 competitors will get points which then will be converted to t-shirts and trips to the finals (here are the rules). This time the problem was written by timmac, I'm just the tester.

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By Nickolas, 9 months ago, translation, In English,

On Friday Topcoder announcement date and location for TCO17 finals — October 20-24, Buffalo, NY.

And today we launched a themed Marathon match WaterfallFishing — rated but without any TCO points. It will run for one week (till May 29), and will have this week's Data Science Weekly Challenge associated with it.

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By Nickolas, 10 months ago, translation, In English,

The second round of TCO17 Marathon Competition AbstractWars started today. It will run for two weeks, and top 30 competitors will get points which then will be converted to t-shirts and trips to the finals (here are the rules). Besides, this round will have two Data Science Weekly Challenges associated with it (which I still have to come up with). I am the writer, enjoy! :-)

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By Nickolas, 11 months ago, translation, In English,

On Saturday, May 7th Topcoder Open returns to Saint-Petersburg, Russia! Event program includes:

  • an onsite round of Algorithm Competition: an SRM-style competition with top-10 participants advancing to the online Wild Card Round on September 16, from which two winners go to TCO finals in undisclosed yet location (rules).
  • T-shirts for all attendees :-)

If you want to participate, register.

Upd. List of registrants

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By Nickolas, 11 months ago, translation, In English,

Incredibly, 34 people managed to solve all problems! 1032 participants solved at least one problem, and it wasn't always A :-)

784A - Numbers Joke

Traditionally the first problem of April Fools Day contest asks to recognize a sequence of integers by problem title and (this time) a single data point. OEIS search for just the given number isn't going to give a result — or rather is going to give too many to be useful. However, if you look for the problem title, the first result for "numbers joke" query will give you https://oeis.org/A006753 "Smith (or joke) numbers", which has 27 as its 3rd element.

784B - Kids' Riddle

This problem is a variation on a kid's riddle in which you have to count closed loops in digits of the number — one in 4, 6, 9 and 0 and two in 8.

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By Nickolas, 11 months ago, translation, In English,

The contest is over; I hope you've enjoyed it :-) Editorial is here.


The fifth April Fools Day Contest will take place on Friday March 31st. This is a joke competition in which solving the problem is often easier than figuring out what the actual task is. Thanks to kit1980 and Codeforces team for their help in preparing problems!

In this round you'll be given 7 weird problems and 2 hours to solve them. The contest will use ACM ICPC rules (no hacks, the standings are decided by the number of solved problems and penalty time earned on them), and it will be unrated. You can submit solutions in any language allowed by Codeforces. To get an idea of what the contest will look like, you can check out the contests of the past years: 2012, 2013, 2014, 2016.

Be warned, to enjoy competing in this round you'll need a sense of humor compatible with mine! Good luck, and have fun!

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Announcement of April Fools Contest 2017
 
 
 
 
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By Nickolas, 12 months ago, translation, In English,

Marathon Match 93 CrossStitch started on March 1st and will run for 2 weeks. I am the writer.

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By Nickolas, 14 months ago, translation, In English,

Marathon Match 92 Lighting started today and will last for 2 weeks. I am the writer :-)

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By Nickolas, 16 months ago, translation, In English,

Marathon Match 91 WanderingTheCity will start on October 19/20 and run for two weeks. The match is very unusual — there is no real-life problem, and there are no prizes or trips to the finals :-) I am the writer.

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By Nickolas, 17 months ago, In English,

A quick update on the status of e-maxx translation project.

First, I'm excited to announce that I've joined e-maxx in English team as an admin! From practical point of view this means that I can review and accept pull requests and help with the issues arising during the contribution process. Feel free to contact me if you have questions. And if I encounter anything outside of my expertise, I can always ping RodionGork directly :-)

Second, October is a particularly good month for contributions to e-maxx translation, as well as for open source contributions in general. Hacktoberfest is back this year, and they are giving away t-shirts to anyone who makes 4 pull requests to any GitHub-hosted projects between October 1st and 31st.

We don't have an explicit list of issues to work on, but there are two basic kinds of contribution we're looking for:

  1. Translations of articles (obviously :-)).
  2. Practice problems for already translated articles — these are the problems at online judges on which the described algorithm can be practiced. See circle-circle intersection article for an example.

Here is a recent post by RodionGork about technical improvements in contributions process.

So if you have at any point considered contributing to e-maxx translation, now is the time to do it :-)

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By Nickolas, 19 months ago, translation, In English,

On Saturday, September 3rd TopCoder Open comes to Saint-Petersburg. Russia! Event highlights include:

  • an onsite round of Algorithm Competition: an SRM-style competition with top-10 participants advancing to the online Wild Card Round, from which two winners go to TCO finals in Washington DC (rules).
  • T-shirts for all attendees :-)
  • if during the next week (till July 22nd) by August 19th the event gathers 100 participants, TopCoder will add a lightning Marathon match with the same rules as for NYC regional event — the Marathon itself takes place before the onsite and is open for everybody to attend, and at the onsite closing ceremony the winners are celebrated. At the moment there are 26 60 94 registrants.

If you want to participate, register, and the sooner the better :-)

Upd. List of registrants

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By Nickolas, 18 months ago, In English,

Here RodionGork started a project to translate http://e-maxx.ru/ into English. Looking at the project now, it looks barely alive — the last commit is almost 6 months old. So I'm curious whether it is still maintained and whether new contributions are welcome.

The reason of my sudden interest is the approaching Hacktoberfest which encourages people to contribute to open source by giving away T-shirts for contributions. This looks like just the thing we need to revitalize the translation :-)

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By Nickolas, 20 months ago, translation, In English,

TCO16 Marathon Round 3 TerrainCrossing started today. It will run for 2 weeks, the top 2 participants will advance to the finals, the top 15 will get t-shirts, and the participants of the first two rounds will finally find out who gets two additional spots in the finals (current unofficial leaderboard). I am the writer; enjoy :-)

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By Nickolas, 20 months ago, In English,

If you like Marathons but don't have two weeks to dedicate to participation in a typical match, consider taking a look at the match that will run for 28 hours right before the TCO16 NYC regional event. The coding phase will start on Thursday, June 16 at 8:00 a.m. EDT (in your time zone) and end on Friday, June 17 at Noon EDT (in your time zone). It will be a rated event featuring a somewhat easier than usual problem (I am the writer ;-)) and following the usual Marathon rules (apart from the shorter duration).

And if you happen to live in New York area, consider not only participating in the Marathon but stopping by at the TCO16 NYC regional event at the Google office afterwards: top participants of this match who will be present at the event will get prizes! Nothing as spectacular as a trip to TCO16 finals, I'm afraid, but I hear it's something quite special :-)

Everyone can participate in the match, but to get the prize you have to be present at the NYC regional event.

UPD: NYC Lightning Round ColorCapture is now live.

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By Nickolas, 21 month(s) ago, translation, In English,

TCO16 Marathon Round 2 StarTraveller started today. It will run for 2 weeks, the top 2 participants will advance to the finals, the top 15 will get t-shirts, and the participants of the first round continue to compete for two additional spots in the finals! The problem was written by JacoCronje.

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By Nickolas, 22 months ago, translation, In English,

All solutions use the same verb definitions to read and write data as the example:

print =: 1!:2&2
read =: 1!:1[3

Besides, the scripts have to end with verb exit ''.

640A - Lazy Caterer Sequence

As usual, the first problem tests competitor's ability to do basic arithmetics. Even in a language so unusual as J arithmetic verbs look pretty standard. Well, except for the fact that in absence of brackets operations are performed right-to-left, without any operator precedence, and division is denoted with %.

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By Nickolas, 23 months ago, translation, In English,

The contest is over; the editorial is available here.


The language of this round is J.

The traditional A+B program (A and B are written in one line and separated with space) looks as follows:

print =: 1!:2&2
read =: 1!:1[3

in =. (read-.LF)-.CR
print +/ ". in

exit ''

The main source of information about the language is http://code.jsoftware.com/wiki/Main_Page. Version used is J804.

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By Nickolas, 23 months ago, translation, In English,

TCO16 Marathon Round 1 CutTheRoots started today. It will run for 2 weeks, the top 2 participants will advance to the finals, and the top 15 will get t-shirts! The idea of the problem is mine, and implementation was done by JacoCronje.

UPD. TopCoder added 2 more spots in the finals! They will go to people who 1) didn't advance to the finals via standard route, 2) took part in all three online rounds and 3) have the lowest sum of ranks in the three rounds.

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