The International Olympiad in Informatics is an annual competitive programming competition for secondary school students. It is the second largest olympiad, after International Mathematical Olympiad, in terms of number of participating countries. The first IOI was held in 1989 in Pravetz, Bulgaria. 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." Students at the IOI compete on an individual basis, with up to four students competing from each participating country. Students in the national teams are selected through national computing contests, such as the Australian Informatics Olympiad, British Informatics Olympiad, Indian Computing Olympiad or Bundeswettbewerb Informatik. The International Olympiad in Informatics is one of the most prestigious computer science competitions in the world. UNESCO and IFIP are patrons.
Competition structure and participation
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 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, or by hand, or by a combination of these means. Pascal will have been removed as an available programming language by 2019.: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 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. 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 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 women participate much more on the national level, claiming sometimes a double-digit percentage of women participate on the first stage. 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." 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.:11 Due to visa issues, the full USA team was unable to attend, although one contestant Zhezheng Luo was able to attend by traveling with the Chinese team and winning gold medal and 3rd place in standings. In IOI 2019 held in Azerbaijan, the Armenia team did not participate due to the dispute between the two countries. For 2020, due to COVID-19 pandemic, the IOI 2020 which will be originally scheduled to host in Singapore in July, is postponed to September, and later converted to online format. Singapore will host the onsite IOI 2021, replacing Egypt which will host IOI 2024.
Summary
All Time Medal Table
Multiple IOI winners
The following is a list of the top performers in the history of the IOI. 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, second and third 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.
Feeder competitions
Most participating countries use feeder competitions to select their team. A number of these are listed below:
