I am attending IOI 2017 and live tweeting IOI 2017. :)

https://twitter.com/jonathanirvings

Once we got the confirmation that IOI 2017 has started, I will upload the problems somewhere :)

Stay tuned.

https://www.youtube.com/watch?v=hI96PiYZndE

Hello!

2017 National Olympiad in Informatics Open Contest has ended. Thank you to everyone who participated the contest.

There were a total of 81 participants :

• 8 of them achieved a score in the bronze cutoff (according to the official 2017 National Olympiad in Informatics).
• 11 of them achieved a score in the silver cutoff (according to the official 2017 National Olympiad in Informatics).
• 19 of them achieved a score in the gold cutoff (according to the official 2017 National Olympiad in Informatics).

Congratulation to wangyenjen for winning the contest. The full result of 2017 National Olympiad in Informatics Open Contest is available here.

The problems are available for upsolving here. We are still working on the problems discussion (editorial), please be patient.

We thank everyone who are involved in 2017 National Olympiad in Informatics :

• ayaze, athin, jonathanirvings, Nekola, radit as Scientific Committee
• afaji321 (problem 1A and 2B), anthonyhkf (problem 2A), athin (problem 0C and 1C), ayaze (problem 0A), chaotic_iak (problem 0B), and jonathanirvings (problem 1B and 2C) as problem setters
• fushar, prabowo and sarusama as problem testers
• fushar as proofreader
• Ivan Hendrajaya, Jordan Fernando, and nathanchrs as Technical Committee

We hope to conduct National Olympiad in Informatics Open Contest again next year, with broader audience. If you have any inquiries, please contact [email protected]. See you next year! :)

Hello!

Indonesia will hold 2017 National Olympiad in Informatics next week (July 3rd — July 5th 2017) in Pekanbaru, Indonesia. It is a competition for Indonesian high school students as one of the preliminary round of Indonesian IOI selection.

And this is the third year for Indonesia (2016, 2015) to invite everyone around the world to try solving the problems by participating the Open Contest! The contest will be conducted on TLX Online Judge. You may need to register for a TLX account if you do not have one. If you have a TLX account, you can login and go to the contest link to register for the contest.

There will be three different contests, one for each day. You may participate them separately (e.g. only participate in Day 1 and Day 2, but not in Day 0), but we expect you to join them all. The Open Contest will start after an hour from the real contest. Here are the schedule and details for the Open Contest:

1. Day 0 (Practice Contest): Monday, July 3rd 15.30 — 24.00 (UTC +7). Register here.
2. Day 1: Tuesday, July 4th 09.30 — 14.30 (UTC +7). Register here.
3. Day 2: Wednesday, July 5th 09.30 — 14.30 (UTC +7). Register here.

The rules of this contest are

• There will be 3 IOI-style problems for each competition day.
• Problem statements will be provided in English and Bahasa Indonesia.
• You can only submit at most 50 submissions for a problem.
• You will get full feedback for each submission.
• For each problem, there are several subtasks:
• For each subtask, there are points assigned to it.
• Each subtask contains several test cases.
• You get the points from that subtask if the program passes all the test cases in that subtask.
• The score of a submission is the sum of all the points that you get from completing subtasks.
• The final score for a problem is the maximum of all the submission scores for that problem.
• Only C++11, C, and Pascal are allowed.
• You will need to read the input from standard input and print the output to standard output.
• You can submit clarification requests in either Bahasa Indonesia or English.
• No medals/certificates will be awarded to Open Contest participants.

NOTE : TLX uses a standard diff to check contestant's output. Therefore, contestant's output must be exactly the same as expected output. (e.g. no extra/missing spaces, no extra/missing newline, etc.). Make sure to print a newline after the last output.

We invite everyone to participate in this contest. See you at the leaderboard.

2017 Indonesian National Olympiad in Informatics Committee

UPD: The problems are available for upsolving here

Will there be an online mirror for ACM ICPC World Finals 2017? Thanks

Hello!

TOKI Open 2017 has ended. Thank you to everyone who participated the contest.

We decided to not consider any participants from the second window whose username is registered on the first window. We also decide to not consider any participants from the second window whose code is very similar to other user's code on the first window. After that, we consider a TOKI Open 2017 participant to be those who made at least one submission on either day.

There were a total of 109 participants, which four of them get a fullscore. Congratulation to Reyna, kevinsogo, pwypeanut, tuna_salad. The full result of TOKI Open 2017 is available here.

The skeletons, solutions, problem descriptions, and testcase generators for TOKI Open 2017 are available here. The problems are available for upsolving here. Alternatively, the PDFs version of the problems are available here (English, Bahasa). The problems discussion (a.k.a. editorial) for TOKI Open 2017 is available here.

We thank everyone who involved in TOKI Open 2017 :

• jonathanirvings, afaji321, athin, and rais.fathin38 as Scientific Committee
• jonathanirvings, afaji321, rais.fathin38, ptrrsn_1, and chaotic_iak as problem setters (the detailed distribution of the problem setters can be seen on the problems discussion)
• ayaze and aguss787 as problem testers
• fushar and Jordan Fernando as TLX developer and Technical Committee.

We hope to conduct TOKI Open again next year, with broader audience. If you have any inquiries, please contact [email protected]. See you next year! :)

The recording of my computer screen during Google Code Jam 2017 Round 1A.

My solution for C-large runs in ceil(A_k/D), which can be up to 10^9 if D=1. It turns out that it is fast enough for one case, but could not run below 8 minutes for 100 testcases (as you can see in my screencast, it is an interesting race between 8 minutes countdown and my program). I downloaded several correct C-large solutions and they also run as slow as mine, but they parallelized the testcases.

TIL : I should add multithreading libraries into my Codejam template.

Hello!

After we successfully organized TOKI Open 2014, we are going to do the similar thing this year. We will open our current IOI Selection Contest to international participants. We call it TOKI Open 2017. TOKI stands for Tim Olimpiade Komputer Indonesia, or Indonesian Computing Olympiad Team in English.

Objectives of us opening this contest include, but not limited to:

• Measure the performance of our IOI trainee compared to other countries' IOI trainee.

• Foster friendship between Indonesia and other IOI participating countries.

• Test Indonesia's scientific committee capability in setting IOI-level problems.

• Test Indonesia's technical committee capability in hosting IOI-level contests.

The contest will have very similar format with IOI, as this contest will be used to select our Top 4 and train our Top 4 for IOI. We expect that the difficulty of the contest is almost the same as IOI. Therefore, this contest is suitable for those who are preparing for IOI. The problems will be available in both Bahasa Indonesia and English.

The rules of TOKI Open 2017 are

• There will be 3 IOI-style problems for each competition day.
• You can only submit at most 50 submissions for a problem.
• You will get full feedback for each submission.
• For each problem, there are several subtasks:
• For each subtask, there are points assigned to it.
• Each subtask contains several test cases.
• You get the points from that subtask if the program passes all the test cases in that subtask.
• The score of a submission is the sum of all the points that you get from completing subtasks.
• The final score for a problem is the maximum of all the submission scores for that problem.
• Unfortunately only C++11 is supported. We will use g++ (Ubuntu 4.8.2-19ubuntu1) 4.8.2 (flags: -std=c++11 -O2 -lm) compiler
• You will only need to implement several functions described in problem statement (i.e. no I/O is needed)
• You can submit clarification requests in either Bahasa Indonesia or English.

The contest will be conducted on TLX Online Judge. You may need to register for a TLX Account if you do not have one. If you have a TLX account, you can login and go to the contest link to register for the contest. There will be two competition days, each having three problems. Each competition day will have two open windows containing the same problemset, so you can participate in either one of the window depending your time preference.

1. Day 1 : Wednesday, 10 May 2017

• Window 1 : 1.30AM — 6.30AM UTC (8.30AM — 1.30PM Western Indonesian Time). Contest Link.
• Window 2 : 12.00PM — 5.00PM UTC (7.00PM — 12.00AM Western Indonesian Time). Contest Link.

1. Day 2 : Friday, 12 May 2017

• Window 1 : 6.30AM — 11.30AM UTC (1.30PM — 6.30PM Western Indonesian Time). Contest Link.
• Window 2 : 12.00PM — 5.00PM UTC (7.00PM — 12.00AM Western Indonesian Time). Contest Link.

A practice contest to get familiarised with TLX and the problem format is available here

IMPORTANT: You are not allowed to register on both windows for the same competition day, since they will have the same problemset. If you have registered on a wrong window, you can go to the contest link to unregister.

We invite everyone (especially eligible IOI participants) to participate in this contest. See you at the leaderboard.

UPD1 : Due to several requests in our country, we have decided to adjust the contest time. The contest will be conducted on 9.00AM — 2.00PM UTC for both competition days. The competition date is remain unchanged (10 May and 12 May). Thank you

UPD2 : Even after we adjust the contest time, we still received several requests. Therefore, we decided to open two windows for both competition days. See the detail on the updated post above. The competition date is remain unchanged (10 May and 12 May). We have thought about this decision carefully and have finalized the schedule. We promise there will not be any future changes to the schedule. Thank you and apologize for the changes.

UPD3 : Detailed rules and practice session posted.

UPD4 : The post-contest post (includes problems repository, problems discussion, etc.) is available here

Hi Codeforces Community,

I would like to invite you to participate in TOKI Open Contest. TOKI Open Contest is our (Indonesian's) monthly/bi-monthly online contest. Starting this month, we have decided to make this contest international :) Every problem is written in both Bahasa Indonesia and English.

TOKI Open Contest February 2017 will be held on Saturday, 18 February 2017, 19.00 — 21.00 Western Indonesian Time (UTC+7). This contest is written by athin, anthonyhkf, aguss787, and jonathanirvings.

Several details related to the contest:

1. The contest will use ACM-ICPC scoring type.

2. There will be FIVE problems with various difficulties but the weight for each problem is the same. The contest time is 2 hours.

3. Any non-Accepted submission will get 8 minutes penalty (but the penalty will only be counted after the respective problem got Accepted)

4. The rank will be sorted according to the most number of solves (problems with Accepted verdict). If there are ties, it will be determined by least (sum of solving time + sum of penalty)

5. The allowed programming languages are C, C++11, Pascal, Python 3, and Java 8. However, please note that we do not ensure that every language can solve all the problems on the given time limit.

6. The contest will be held on https://competition.ia-toki.org/contests/161. Registration is already opened at the same place. Registering the contest requires a TLX (http://competition.ia-toki.org) account. You may need to register for an account if you don't have one.

Good luck and have fun! See you at the leaderboard! :)

UPDATE 1 : Less than 24 hours to the start of the contest :) Make sure you have registered :)

UPDATE 2 :

The contest is over, thanks for participating the TOKI Open Contest February 2017! :D This contest has 97 contestants with at least one submission.

The following are the winner of the TOKI Open Contest February 2017:

1. ayaze solved 5 problems with 305 minutes total penalty

2. rais.fathin38 solved 5 problems with 346 minutes total penalty

3. [john] solved 4 problems with 220 minutes total penalty

Congratulation to winners! :D

The problems are available at https://training.ia-toki.org/problemsets/73/problems for upsolving. See you at the next TOKI Open Contest! :D

I am a football fan. If you are also, then you probably have known that yesterday is a very sad day for football.

Brazilian football club Chapecoense lost almost all of their players when the plane carrying the squad crashed in Colombia. The team was en route to play one of the most prestigious tournament in South America when the accident happened.

This is not the first time a plane carrying the squad of a football club crashed. In 1958, the plane carrying the English champion Manchester United FC crashed when the team was returning from a match, killing majority of the team.

Let us pray for the victims involved in the accident. Also, let us pray and hope that similar accident will not happen in the competitive programming community, as a lot of us (including myself) will be flying a lot for ACM-ICPC Regional in this September-December period, and for other competitions as well.

Safe trip for all of us.

I don't know whether it is only for me, but I have an issue with Codeforces Blog.

When you want to edit your blog, at the (almost) end of the page, there are 4 buttons : "Post", "Discard", "Save draft", "Preview". The rest of the buttons seems trivial, but I have an issue with the "Discard" button.

The "discard" button looks like "discard the edit" for me, which means "my edit will be discarded, thus everything that I type will be ignored and my blog will stay as before". However, that's not the case. The "discard" button here actually means "delete the blog".

I have accidentally deleted two blogs because of this issue. But I don't know, is it only me?

Hi all Codeforces members,

I would like to invite you to participate in the online mirror of 2015 ACM ICPC Asia Singapore Regional. It will be available on Kattis. The online mirror will start (and end) 15 minutes later than the original contest. The problems are interesting! :) Thanks Kattis team for supporting this event.

Meanwhile, we will provide the live commentary for the onsite contest. I will broadcast the detail and the URL of the scoreboard later. Stay tuned! :)

UPDATE

The public scoreboard will be available on https://asiasg15.kattis.com/standings. It will start tomorrow on 9AM SGT (1AM UTC).

Guess what? We will also provide live stream commentary on Youtube! (yeay, it's like World Finals). The live stream will be available on https://www.youtube.com/user/jonathanirvings/live one hour after the contest starts (10AM SGT), discussing mainly problem discussions, contest scoreboard, and a lot of other things. We will also provide commentary text on twitter using @NUSComputing account and ‪#‎icpcsg‬ hashtag.

I'm sorry for my curiosity, but I really would like to know.

What happens to Žiga Željko in IOI 2015?

I remember he gets 100 in problem scales very quickly but not long after that, his submission becomes 0. In IOI stats page, his score are dashes (-).

I believe he is accused to be cheating. Can anyone (especially ISC, or those who attend GA) confirm this? What did he do?

My live commentary of the second day of IOI 2015 is available here

I will live comment day 1 of IOI 2015. It will be avaiable here

I created this post a year ago (wew, I didn't realise it's already a year) after WF 2014, but I accidentally deleted it just now :'(

=====BEGIN OF POST A YEAR AGO=====

Here are several photos of me with famous people I met in ACM ICPC World Finals 2014. It is a great honour to met these people :)

I think everybody in this forum know who he is :)

me with tourist. As we know, he isn't competing this year, and I don't know what is he doing here. :p This is the second time I took picture with him. I took a picture with him two years ago in IOI 2012 :)

me with misof.

me with Egor.

me with yeputons. One of the member of St. Petersburg State University (the champion) team.

me with subscriber.

There are also other several 'targets', but I didn't manage to get the photo with them :'(

=====END OF POST A YEAR AGO=====

but I didn't manage to get the photo with them :'(

This year (2015), I am also in ICPC World Finals and I managed to take more photos with people that I didn't manage to get the photo with :)

me with andrewzta, coach of SPB SU ITMO.

More photos coming :')

http://jonathanirvings.com/2014/06/acm-icpc-world-finals-2014/ :)

I accidentally discard the original post :'( Luckily I have the backup :) (but all of the comments are gone, though :( ). Let me repost it.

My target : Being red in TopCoder (or Codeforces also OK) before ACM-ICPC World Finals 2014. I remember watching live scoreboard of last year's ICPC WF in ahmed_aly's site. In that site, beside the team's name, there are the TC handles of the team's members. I want to make my handle red :p

Story : 12 June 2014 (1.5 weeks before ICPC WF), my TopCoder rating is 2182. There are still two more SRMs before WF. One of them, TopCoder SRM 624 was at that night. I failed it because of stupid MOD issue :'( (At practice mode, I resubmit after fixing that issue and got AC). I was very depressed, as I really want to be red that night. (If I got AC, I would be top 100 and definitely be red) My rating decreased to 2138.

Switch to Codeforces. My Codeforces rating was 2131. I participated Zepto Code Rush yesterday without any desire to make it red. But unpredictably, I got +72 and become red in Codeforces :') I take this as a comeback! (I failed several last rounds, including SRM624 and GCJ Round 2) I will keep this rating until World Finals (I will rest from Codeforces until WF) :)

PS : This comeback will be complete if I can make my TopCoder handle red at the last SRM before WF, TopCoder SRM 625 :))

Update : Comeback complete. I was ranked 29 in SRM625 and become red coder! :)

Hello,

Following this comment and this post, let's collect the handles of the participants of ACM-ICPC World Finals 2014 :)

I will start with the data from PavelKunyavskiy's data in this comment. (big thanks for him).

EDIT : I decided to move it here

Please comment below to add your team (or your friend's team) to make the data complete. Please also comment below if you find any inaccurate data.

Thanks :)

As you may know, Codeforces Round #192 was written by Indonesians: dolphinigle, fushar, and me.

For dolphinigle, this is his fourth contest in Codeforces. For fushar, this is his first contest in Codeforces, but he already wrote several problems in TopCoder SRM.

For me, this is my first 'international' contest. I never wrote a problem in both Codeforces and TopCoder before. I think my 'writing' skill isn't enough yet :(

So, in this post, I would like to personally thank dolphinigle and fushar, for giving me the experience of writing an 'international' contest. Without them, I won't write such an amazing round (at least, not now). How can I write Div-1 problems... :|

Once again, thanks a lot :)

PS : My contribution to that contest is only Div-2 problem. If you like the contest because of Div-1 problems (e.g. the "special output-only" Div1-D), thank them :)

I uploaded my photos in IOI2013 on Google+. I didn't have time to filter them, so I upload all of them :))

https://plus.google.com/photos/118191331024263100931/albums/5900295760575181489

Enjoy :)