IOI 2018 took place in Japan in September, 2018. More info is available on the official website.
Just happened IOI 2018 in Japan
The 12th International Olympiad in Informatics was held in Beijing, China in 2000. 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.
Building with Blocks
Test cases and some source codes
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.