International Olympiad in Informatics

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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.

Each country sends a team of up to four students, plus one team leader, one deputy leader, and guests. 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 contest consists of two days of solving six complicated algorithmic tasks by writing computer programs in C++.^[1][2] All task materials are published on each year's contest website soon after the competition ends.

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A bronze medal from IOI 2006 in Mexico

On each of the two competition days, the competitors are typically given three problems which they have to solve in five hours. Each student works on their own to solve the problems with no outside help, specifically no communication with other contestants, books, web access, etc. Contestants are typically allowed to bring no programable wired keyboards and mice.^[3] Usually to solve a task the contestant has to write a computer program (in C++) and submit it before the five-hour competition time ends. The program is graded based on secret test data. Since 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 (a.k.a interactive problems). Another type of problem has the inputs publicly available, 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.^[4]: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.^[5]

The scores from the two competition days and all problems are summed up separately for each contestant. Medals are awarded 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, 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.^[6] President of the IOI (2011-2014), 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] The European Girls’ Olympiad in Informatics (EGOI), which was first held in 2021 was started with the goal to increscent female participants at IOI and other Informatics Olympiads.^[7]

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.^[4]:11 Due to visa issues, the full USA team was unable to attend, although one contestant Zhezheng Luo^[8] was able to attend by traveling with the Chinese team^[9] and winning gold medal and 3rd place in standings.^[10]

In IOI 2019 held in Azerbaijan, the Armenia team did not participate due to the dispute between the two countries, despite the guarantees provided^[11] 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.^[12]

In response to the invasion of Ukraine, students from Russia and Belarus can only participate as individuals under the IOI flag but not as national delegations starting from IOI 2022, and they would only participate online for IOI 2022, but they may return on-site from IOI 2023 onwards.^[13]

In response to the conflict and humanitarian crisis in Gaza, students from Israel can only participate as individuals under the IOI flag but not as a national delegation from IOI 2025 onwards. Over two thirds of the delegations voted in favour of the sanction in the IOI General Assembly.^[14]

Number	Year	Dates	Host country	Host city	Results	Website
1	1989	May 16–19	Bulgaria	Pravetz	[15]
2	1990	July 15–21	Belarus, Soviet Union	Minsk	[16]
3	1991	May 19–25	Greece	Athens	[17]
4	1992	July 11–21	Germany	Bonn	[18]
5	1993	October 16–25	Argentina	Mendoza	[19]	[20]
6	1994	July 3–10	Sweden	Haninge	[21]	[22]
7	1995	June 26 – July 3	Netherlands	Eindhoven	[23]
8	1996	July 25 – August 2	Hungary	Veszprém	[24]
9	1997	November 30 – December 7	South Africa	Cape Town	[25]
10	1998	September 5–12	Portugal	Setúbal	[26]
11	1999	October 9–16	Turkey	Antalya-Belek	[27]
12	2000	September 23–30	China	Beijing	[28]
13	2001	July 14–21	Finland	Tampere	[29]
14	2002	August 18–25	Korea Rep.	Yong-In	[30]
15	2003	August 16–23	United States	Kenosha, Wisconsin	[31]
16	2004	September 11–18	Greece	Athens	[32]
17	2005	August 18–25	Poland	Nowy Sącz	[33]	[34]
18	2006	August 13–20	Mexico	Mérida, Yucatán	[35]
19	2007	August 15–22	Croatia	Zagreb	[36]	[37]
20	2008	August 16–23	Egypt	Cairo	[38]
21	2009	August 8–15	Bulgaria	Plovdiv	[39]	[40]
22	2010	August 14–21	Canada	Waterloo, Ontario	[41]	[42]
23	2011	July 22–29	Thailand	Pattaya	[43]	[44]
24	2012	September 23–30	Italy	Sirmione and Montichiari	[45]	[46]
25	2013	July 6–13	Australia	Brisbane	[47]	[48]
26	2014	July 13–20	Taiwan	Taipei	[49]	[50]
27	2015	July 26 – August 2	Kazakhstan	Almaty	[51]	[52]
28	2016	August 12–19	Russia	Kazan	[53]	[54]
29	2017	July 28 – August 4	Iran	Tehran	[55]	[56]
30	2018	September 1���8	Japan	Tsukuba	[57]	[58]
31	2019	August 4–11	Azerbaijan	Baku	[59]	[60]
32	2020	September 13–19a	Singapore	online	[61]	[62]
33	2021	June 19–25	Singapore	online	[63]	[64]
34	2022	August 7–15	Indonesia	Yogyakarta	[65]	[66]
35	2023	August 28 – September 4	Hungary	Szeged	[67]	[68]
36	2024	September 1–8	Egypt	Alexandria	[69]	[70]
37	2025		Bolivia	La Paz		[71]
38	2026		Uzbekistan			[72]
39	2027		Germany	Potsdam

As of 2023

Rank	Nation	Gold	Silver	Bronze	Total
1	China (CHN)	100	27	12	139
2	Russia (RUS)	68	40	12	120
3	United States (USA)	65	38	16	119
4	South Korea (KOR)	48	47	28	123
5	Poland (POL)	42	50	35	127
6	Japan (JPN)	35	28	10	73
7	Romania (ROU)	33	58	36	127
8	Iran (IRN)	31	65	23	119
9	Bulgaria (BGR)	27	51	45	123
10	Taiwan (TWN)	25	61	27	113
Totals (10 entries)		474	465	244	1,183

The following is a list of the top performers in the history of the IOI.^[73] 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.

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

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

• List of computer science awards
• International Science Olympiad
• International Collegiate Programming Contest
• Central European Olympiad in Informatics
• Competitive programming
• International Mathematical Olympiad

Wikimedia Commons has media related to International Olympiad in Informatics.

• International Olympiad in Informatics (IOI) community Archived 2022-01-16 at the Wayback Machine (hosted on Commonlounge)
• IOI International Committee Website
• IOI Statistics
• IOI Secretariat Website