Call for Tasks

The IOI 2023 Host Scientific Committee (HSC) is pleased to invite the IOI community
to participate in the design of the IOI 2023 competition tasks.

Competition Task

IOI tasks are typically focused on the design of efficient, correct algorithms.
Input and output are to be kept as simple as possible.
The IOI needs both simple and hard tasks that are creative,
so if some of your designed tasks seem easy but creative please submit them too.

The competition tasks from previous IOIs can provide, by example,
good guidance on the desired composition of tasks:

However, the nature of previous tasks should not constrain the design of new tasks;
the submission of novel task types not yet seen in IOIs are encouraged.
We are particularly interested in tasks whose basic rules (if not optimal strategy)
are accessible to a wide audience, and tasks that illustrate algorithms and
computational problems that arise in a variety of human endeavours.
Open-ended tasks, ones that do not necessarily have a known efficient or optimal solution,
are welcome.

We are also particularly interested in tasks that go beyond the typical format
in which a program collects input, performs some computation, and returns output.
Examples include “reactive” and “output only” tasks which have been used occasionally
in previous IOIs. Tasks with some measure of solution effectiveness
other than CPU time consumption are encouraged.

A syllabus listing the material generally considered acceptable for IOI tasks
can be found at
The syllabus is not meant to be restrictive, but to serve as a guideline for task preparation.

To ensure a fair and interesting competition for all, tasks should satisfy the following conditions:

  • the tasks should not have been seen by any potential IOI 2023 contestants;
  • the tasks should not have been used in any recent similar competition;
  • the tasks should be solvable by IOI competitors during an IOI contest round;
  • the task descriptions should be unambiguous and easy to understand;
  • the tasks should be original and/or innovative.

For further reading, the ISC procedures and policies
document contains a brief description of the task selection process applied by the ISC over the recent years.

Task Criteria

A task submission must contain:

  • Statement in English, preferably formatted in PDF with required diagrams and pictures included.
  • Description of the desired solution (a description of an algorithm which should get full score).
  • Contact address (preferably one e-mail address) and background information on the task author(s): affiliation, country, and a description of the author’s role in the IOI or national olympiad, including training duties, over the period from IOI 2021 to IOI 2023.
  • If you want to recieve a feedback from the ISC on your submission, you should also provide a PGP key ID along with the submission.

It is also strongly recommended to contain:

  • At least one implementation of the desired solution in C++.
  • Analyses of alternative solutions.
  • Suggestions for grading.
  • Test data or ideas for generating test data.
  • The motivation behind the task.

Any comments related to the task are also welcome and would be highly appreciated.

Submitted tasks must be kept in strict confidence until the end of IOI 2023.
After that, authors are free to do whatever they wish with the tasks
but may be asked to have them considered for IOI 2024, in which case strict confidence
would have to be maintained through until IOI 2024.

Submission Process

Task materials must be placed together in a single file (use .zip or .tgz for multiple files)
and submitted online at
When submitting a task, you will have to enter the authorisation code “halaszle”.
Please do not encrypt your submission: the upload page will do this automatically.


Please note that by submitting the task, the author asserts that he or she is authorised to grant,
and does grant IOI an exclusive license to use the material until September 30, 2023,
and a perpetual non-exclusive transferable license to reproduce the material.
The author warrants that the requirements in this call for submissions are met,
and that the materials will not be disclosed to any third party
for the duration of the exclusive license.

Task authors and their collaborators must not use a submitted task, or a variant thereof,
or techniques specific to that task, in any competition or training until IOI 2023 has ended.
In case of doubt, contact the ISC. Note that we do not wish to forbid
authors of submitted tasks to be involved in other competitions and training,
but we do ask them to take all necessary precautions to safeguard confidentiality.

What Happens Next

Receipt of submissions will be confirmed via the provided contact address.
The Scientific Committee will carefully review all submissions and will select a
short-list of around 10 tasks, six of which will eventually be given at the IOI 2023 competition.

The authors of the tasks selected for the short-list will be invited to attend the
IOI 2023 in Hungary as Invited Guests (authors will be responsible for their travel,
but IOI 2023 will cover their stay). However, they will not be informed prior to the competition
as to whether their tasks will be used at the actual contest, or whether the
Scientific Committee has substantially modified their tasks.
In case the task authors are ineligible to be invited or the task authors reject the invitation,
they will be awarded IOI 2023 souvenirs (including, but not limited to T-shirts) by mail.

The authors of all submitted tasks will receive feedbacks from the ISC.
The authors of tasks included in the actual competition will also be recognised by listing
their name, affiliation and country on the official IOI website
(unless they specifically decline this). The problems of tasks included in the actual competition
will be made available under a Creative Commons Attribution license (CC-BY).


  • Submission deadline: Sunday, 11 December 2022 Sunday, 29 January 2023
  • Language: English
  • Text format: PDF preferred
  • Multiple files for one task (e.g. diagrams, solution code): in a single zip or compressed tar archive
  • Multiple tasks: submit separately
  • Minimum contents of submission:
    • author(s) information: name, e-mail, affiliation, country, and olympiad-role;
    • task statement;
    • description of the desired solution.
  • Also recommended: solution implementations in C++;
    • suggestions for grading;
    • test data;
    • alternate solutions or expected near-solutions;
    • background information on the task;
    • any other comments relevant to the task.
  • Submission site: The authorisation code is “halaszle”.

Please direct questions about the call for tasks to