Due to the COVID-19 pandemic, IOI 2020 will be held online. More info is available on the official website.
Update IOI 2020 will be held online
The 16th International Olympiad in Informatics was held in Athens, Greece in 2004. There were two competition days, with 3 tasks given to the competitors on each day. You can see the tasks, test cases and solutions below.
Solutions to all problems
Note that the grading model changed at IOI'94 and beyond.
Before IOI 1994, a human evaluator would sit behind the competitor's computer and do the testing manually (enter test data through the keyboard, check the output on the screen). Starting from IOI 1994, an automatic grading process is used, with test input defined in files.