IOI 2018 took place in Japan in September, 2018. More info is available on the official website.
Just happened IOI 2018 in Japan
The 9th International Olympiad in Informatics was held in Cape Town, South Africa in 1997. There were two competition days, with 3 tasks given to the competitors on each day. You can see the tasks and solutions below.
Game of Hex
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.