International Olympiad in Informatics

The International Olympiad in Informatics (IOI) is an annual competitive programming and one of the International Science Olympiads for secondary school students. It is the second largest science olympiad, after International Mathematical Olympiad, in terms of number of participating countries (83 at IOI 2017). 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 (with 81 countries in 2012). Students in the national teams are selected through national computing contests, such as the Australian Informatics Olympiad, British Informatics Olympiad, Indian Computing Olympiad or the Canadian Computing Olympiad.

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

Contest structure

• 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 will have been removed as an available programming language by 2019.
• 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).