The 31st International Olympiad in Informatics was held in Baku, Azerbaijan in 2019. 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.

Day 1:
      Arranging Shoes
      Split the Attractions
      Rectangles

Day 2:
      Broken Line
      Vision Program
      Sky Walking

Other materials:
      Test cases
      Solutions to all problems
      Practice 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.