On creating and setting interactive problems

Revision en2, by bensonlzl, 2020-02-22 19:39:18

Hi Codeforces,

Interactive problems prop up regularly in Codeforces contests nowadays, and are a staple in IOI (2013 Cave, 2016 Messy, 2017 Prize and Simurgh, 2018 Combo and Highways). These sort of problems usually involve (1) something hidden that the solution needs to find in (2) a limited number of queries that provide specific information. Some of these are more ad-hoc than others that also incorporate more standard algorithms.

In the Singapore CP community, I make interactive problems every once in a while for the online judge that we use (no links because we prefer to keep it within SG :P). Here are some examples of interactive problems that I have made over the past year or so (without solutions)


Usually when I make an interactive problem, I either start with some puzzle or some game and turn it into a problem. The problem evolves over time as I add and remove conditions until I reach a problem that I am satisfied with.

To all the problem-setters out there that create and set interactive problems for various contests:

  1. What are your thought processes as you start from an initial idea and end at the final problem?

  2. What characteristics / ideas do you look out for in good interactive problems?

Tags interactive, interactive problem, problemsetting


  Rev. Lang. By When Δ Comment
en2 English bensonlzl 2020-02-22 19:39:18 7 (published)
en1 English bensonlzl 2020-02-22 19:38:40 4755 Initial revision (saved to drafts)