International Olympiad in Informatics

The International Olympiad in Informatics (IOI) is an annual competitive programming competition and one of the International Science Olympiads for secondary school students. The first IOI was held in 1989 in Pravetz, Bulgaria. It is the second largest science olympiad, after the International Mathematical Olympiad, in terms of number of participating countries (88 at IOI 2022). Each country sends a team of up to four students, plus one team leader, one deputy leader, and guests.

The logo of the International Olympiad in Informatics

The contest consists of two days of computer programming/coding and problem-solving of algorithmic nature. To deal with problems involving very large amounts of data, it is necessary to have not only programmers, "but also creative coders, who can dream up what it is that the programmers need to tell the computer to do. The hard part isn't the programming, but the mathematics underneath it."[1]

Students in each country are selected for their country's team through national computing contests. Students at the IOI compete on an individual basis. There is no official team ranking.

The IOI is one of the most prestigious computer science competitions in the world. UNESCO and IFIP are patrons.

Competition structure and participation
The competition room at the IOI 2006
Front
Back
A bronze medal from IOI 2006 in Mexico
In front of the competition room at the IOI 2007

On each of the two competition days, the students are typically given three problems which they have to solve in five hours. Each student works on his/her own, with only a computer and no other help allowed, specifically no communication with other contestants, books etc. Usually to solve a task the contestant has to write a computer program (only in C++) and submit it before the five-hour competition time ends. The program is graded by being run with secret test data. From IOI 2010, tasks are divided into subtasks with graduated difficulty, and points are awarded only when all tests for a particular subtask yield correct results, within specific time and memory limits. In some cases, the contestant's program has to interact with a secret computer library, which allows problems where the input is not fixed, but depends on the program's actions – for example in game problems. Another type of problem has known inputs which are publicly available already during the five hours of the contest. For these, the contestants have to submit an output file instead of a program, and it is up to them whether they obtain the output files by writing a program (possibly exploiting special characteristics of the input), or by hand, or by a combination of these means. Pascal has been removed as an available programming language as of 2019.[2]:11

IOI 2010 for the first time had a live web scoreboard with real-time provisional results. Submissions will be scored as soon as possible during the contest, and the results posted. Contestants will be aware of their scores, but not others', and may resubmit to improve their scores. Starting from 2012, IOI has been using the Contest Management System (CMS) for developing and monitoring the contest.

The scores from the two competition days and all problems are summed up separately for each contestant. At the awarding ceremony, contestants are awarded medals depending on their relative total score. The top 50% of the contestants are awarded medals, such that the relative number of gold : silver : bronze : no medal is approximately 1:2:3:6 (thus 1/12 of the contestants get a gold medal).

Prior to IOI 2010, students who did not receive medals did not have their scores published, making it impossible for a country to be ranked by adding together scores of its competitors unless each wins a medal. From IOI 2010, although the scores of students who did not receive medals are still not available in the official results, they are known from the live web scoreboard. In IOI 2012 the top 3 nations ranked by aggregate score (Russia, China and USA) were subsequently awarded during the closing ceremony.

Analysis of female performance shows 77.9% of women obtain no medal, while 49.2% of men obtain no medal. "The average female participation was 4.4% in 1989–1994 and 2.2% in 1996–2014." It also suggests much higher participation of women on the national level, claiming sometimes double-digit percentages in total participation on the first stage.[3] President of the IOI, Richard Forster, says the competition has difficulty attracting women and that in spite of trying to solve it, "none of us have hit on quite what the problem is, let alone the solution."[1]

In IOI 2017 held in Iran, due to not being able to participate in Iran, the Israeli students participated in an offsite competition organized by IOI in Russia.[2]:11 Due to visa issues, the full USA team was unable to attend, although one contestant Zhezheng Luo[4] was able to attend by traveling with the Chinese team[5] and winning gold medal and 3rd place in standings.[6]

In IOI 2019 held in Azerbaijan, the Armenia team did not participate due to the dispute between the two countries, despite the guarantees provided[7] and official invitation letter sent by the host Azerbaijan.

Due to the COVID-19 pandemic, both the IOI 2020 and IOI 2021, originally scheduled to be hosted by Singapore, were held as online contests. The IOI 2022, hosted by Indonesia, was held as a hybrid event, with around 25% of the contestants participating online.[8]

Summary
NumberYearDatesHost countryHost cityResultsWebsite
11989May 16–19Bulgaria BulgariaPravetz[9]
21990July 15–21Byelorussian Soviet Socialist Republic Belarus, Soviet UnionMinsk[10]
31991May 19–25Greece GreeceAthens[11]
41992July 11–21Germany GermanyBonn[12]
51993October 16–25Argentina ArgentinaMendoza[13][14]
61994July 3–10Sweden SwedenHaninge[15]
71995June 26 – July 3Netherlands NetherlandsEindhoven[16]
81996July 25 – August 2Hungary HungaryVeszprém[17]
91997November 30 – December 7South Africa South AfricaCape Town[18]
101998September 5–12Portugal PortugalSetúbal[19]
111999October 9–16Turkey TurkeyAntalya-Belek[20]
122000September 23–30China ChinaBeijing[21]
132001July 14–21Finland FinlandTampere[22]
142002August 18–25South Korea Korea Rep.Yong-In[23]
152003August 16–23United States United StatesKenosha, Wisconsin[24]
162004September 11–18Greece GreeceAthens[25]
172005August 18–25Poland PolandNowy Sącz[26][27]
182006August 13–20Mexico MexicoMérida, Yucatán[28]
192007August 15–22Croatia CroatiaZagreb[29][30]
202008August 16–23Egypt EgyptCairo[31]
212009August 8–15Bulgaria BulgariaPlovdiv[32][33]
222010August 14–21Canada CanadaWaterloo, Ontario[34][35]
232011July 22–29Thailand ThailandPattaya[36][37]
242012September 23–30Italy ItalySirmione and Montichiari[38][39]
252013July 6–13Australia AustraliaBrisbane[40][41]
262014July 13–20Taiwan TaiwanTaipei[42][43]
272015July 26 – August 2Kazakhstan KazakhstanAlmaty[44][45]
282016August 12–19Russia RussiaKazan[46][47]
292017July 28 – August 4Iran IranTehran[48][49]
302018September 1–8 Japan JapanTsukuba[50][51]
312019August 4–11Azerbaijan AzerbaijanBaku[52][53]
322020September 13–19aSingapore Singaporeonline[54][55]
332021June 19–25Singapore Singaporeonline[56][57]
342022August 7–15Indonesia IndonesiaYogyakarta[58][59]
352023August 28 – September 4Hungary HungarySzeged[60][61]
362024September 1–8Egypt EgyptAlexandria[62]
372025Bolivia BoliviaLa Paz[63]
382026Uzbekistan Uzbekistan

All-time medal table
As of 2023
RankNationGoldSilverBronzeTotal
1 China (CHN)1002712139
2 Russia (RUS)684012120
3 United States (USA)653816119
4 South Korea (KOR)484728123
5 Poland (POL)425035127
6 Japan (JPN)35281073
7 Romania (ROM)335836127
8 Iran (IRN)316523119
9 Bulgaria (BUL)275145123
10 Taiwan (TWN)256127113
Totals (10 entries)4744652441183

Multiple IOI winners

The following is a list of the top performers in the history of the IOI.[64] The P sign indicates a perfect score, a rare achievement in IOI history. The U sign indicates an unofficial participation, where a contestant participated in a host's second team. Also, first (I), second (II) and third (III) places among gold medalists are indicated where appropriate. This list includes only those countries where the national selection contest allows the same participant to go multiple times to the IOI.

NameTeamYears
Gennady KorotkevichBelarusG(II) 2012GP(I) 2011G(I) 2010G(I) 2009G 2008G 2007S 2006
Zixiang ZhouCanadaG 2022G 2021G 2020G(III) 2019S 2018
Hristo VenevBulgariaG 2016G 2015G 2014G 2013S 2012
Filip WolskiPolandG(I) 2006G 2005G 2004G 2003
Yuta TakayaJapanG(I) 2017G 2016G 2015G 2014
Rareș Darius BuhaiRomaniaG 2015G 2014G 2013G 2012
Rumen HristovBulgariaG 2012G 2011G(II) 2010S 2009S 2008
Andrzej Gąsienica-SamekPolandG 1999G 1998G 1997S 1996
Martin PettaiEstoniaG 2002G 2001G 2000S 1999
Eduard BatmendijnSlovakiaG 2015G 2013G 2012S 2014
Nikoloz BirkadzeGeorgiaG 2020G 2019G 2018S 2017
Patrick PavićCroatiaG 2022G 2021G 2020S 2019
Vladimir MartianovRussiaG 1999GP(I) 1998G(I) 1997
Scott WuUnited StatesGP(I) 2014G 2013G 2012
Martin MarešCzech RepublicG 1995G 1994G(I) 1993
John PardonUnited StatesG 2007G 2006G 2005
Marcin AndrychowiczPolandG 2008G 2007G 2006
Neal WuUnited StatesG 2010G 2009G 2008
Shogo MuraiJapanG 2012G 2011G 2010
Jarosław KwiecieńPolandG 2016G 2015G 2014
Vladimir RomanovRussiaG 2019G 2018G 2017
Masataka YonedaJapanG 2020G 2019GU 2018
Daiki KodamaJapanG 2023G 2022G 2021
Encho MishinevBulgariaG 2017G 2014S 2016S 2015S 2013
Egor LifarRussiaG 2021G 2019S 2020S 2018S 2017
Alex SchwendnerUnited StatesG 2005G 2003S 2004S 2002
Wolfgang ThallerAustriaG 1997G 1996S 1999S 1998
Bruce MerrySouth AfricaG 2001G 2000S 1999B 1998B 1997B 1996
Harris LeungHong KongG 2021G(III) 2020S 2019B 2018B 2017
Goran ŽužićCroatiaG 2008G 2007S 2009B 2006
Vlad Alexandru GavrilăRomaniaG 2013G 2012S 2011B 2010
Dorijan LendvajCroatiaG 2022G 2021S 2020B 2019

Feeder competitions

Most participating countries use feeder competitions to select their team. A number of these are listed below:

Further information: National Olympiad in Informatics

Notes
1.^a IOI 2020 virtual closing ceremony was held on September 23, 2020.

See also

References
  1. Robson, Frank (10 August 2013). "Numbers game". The Sydney Morning Herald. Retrieved 17 August 2013.
  2. "Minutes of the Meetings held in Kazan, Russian Federation" (PDF). ioinformatics.org. General Assembly of International Olympiad in Informatics. 19 August 2016. pp. 7, 11.
  3. Maggiolo, Stefano (2015). "An Update on the Female Presence at the IOI" (PDF). Olympiads in Informatics. London, U.K.: ioinformatics.org. 9, 127–137 (2015): 127–137. doi:10.15388/ioi.2015.10. Retrieved 13 July 2017.
  4. "Zhezheng Luo". stats.ioinformatics.org.
  5. Simões, Gabriel (31 July 2017). "IOI 2017, first round - Codeforces". Codeforces. Retrieved 4 August 2017. There is really only one USA contestant on site, it looks like he came with the Chinese team (straight from China).
  6. "IOI 2017: Results". stats.ioinformatics.org.
  7. "General Assembly Minutes of the Meetings held in Almaty, Kazakhstan 26 July – 2 August, 2015" (PDF).
  8. "Number of Participants". ioi2022.id.
  9. "IOI 1989 Results".
  10. "IOI 1990 Results".
  11. "IOI 1991 Results".
  12. "IOI 1992 Results".
  13. "IOI 1993 Results".
  14. "IOI 1993 Website". ioi1993.
  15. "IOI 1994 Results".
  16. "IOI 1995 Results".
  17. "IOI 1996 Results".
  18. "IOI 1997 Results".
  19. "IOI 1998 Results".
  20. "IOI 1999 Results".
  21. "IOI 2000 Results".
  22. "IOI 2001 Results".
  23. "IOI 2002 Results".
  24. "IOI 2003 Results".
  25. "IOI 2004 Results".
  26. "IOI 2005 Results".
  27. "IOI 2005 Website". ioi2005.
  28. "IOI 2006 Results".
  29. "IOI 2007 Results".
  30. "IOI 2007 Website". ioi2007.
  31. "IOI 2008 Results".
  32. "IOI 2009 Results".
  33. "IOI 2009 Website". ioi2009.org.
  34. "IOI 2010 Results".
  35. "IOI 2010 Website". ioi2010.org.
  36. "IOI 2011 Results".
  37. "IOI 2011 Website". ioi2011.
  38. "IOI 2012 Results".
  39. "IOI 2012 Website". ioi2012.org.
  40. "IOI 2013 Results".
  41. "IOI 2013 Website". ioi2013.org.
  42. "IOI 2014 Results".
  43. "IOI 2014 Website". ioi2014.org.
  44. "IOI 2015 Results".
  45. "IOI 2015 Website". ioi2017.kz.
  46. "IOI 2016 Results".
  47. "IOI 2016 Website". ioi2016.ru.
  48. "IOI 2017 Results".
  49. "IOI 2017 Website". ioi2017.org.
  50. "IOI 2018 Results".
  51. "IOI 2018 Website". ioi2018.jp.
  52. "IOI 2019 Results".
  53. "IOI 2019 Website". ioi2019.az.
  54. "IOI 2020 Results".
  55. "IOI 2020 Website". ioi2020.sg.
  56. "IOI 2021 Results".
  57. "IOI 2021 Website". ioi2021.sg.
  58. "IOI 2022 Results".
  59. "IOI 2022 Website". ioi2022.id.
  60. "IOI 2023 Results".
  61. "IOI 2023 Website". ioi2023.hu.
  62. "IOI 2024 Website". ioi2024.eg.
  63. "IOI 2025 Website". ioi2025.bo.
  64. "Hall of Fame". stats.ioinformatics.org.
  65. http://olimpiada.info/Romanian National Informatics Olympiad Archived 2019-06-24 at the Wayback Machine
  66. "Informatica Olympiade".
  67. "Home — NOI.PH".
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