Competition Rules

Competition Schedule

There will be two competition days, see the Schedule. On each day contestants will be given four tasks to solve in 5 hours. The tasks will be in random order, that is tasks are not sorted by difficulty. The task will be sorted by difficulty as perceived by the scientific committee. Note that contestants might disagree with the order so we suggest they read all problems. Remember that hard problems can have easy subtasks.

Practice Session

There will be a 3-hour Practice Competition prior to the first competition day to familiarise all contestants with the grading system and contest environment. The practice tasks will be published before the EGOI. Contestants may bring printed solutions to the practice tasks, on paper only, during the Practice Competition.

Contestants may bring some of the following items to the practice session:

After the practice session, the items must be left at the competition site if the contestants want to use them during the real contest. It is forbidden to bring these items directly to the competition days. See the Supplies section below for more details.


Gold, silver and bronze medals will be awarded to the contestants so that approximately 50 percent of all European contestants receive a medal and the ratio of gold to silver to bronze medals is approximately 1:2:3. For more details, see the EGOI regulations.

Competition Equipment and Environment

Contestants will be provided with a computer set up with a virtual machine. Please refer to the Contest Environment page for more details. This virtual machine must be run at full-screen mode at all times, except when solving a technical issue as instructed by the Technical Committee.

Documentation for C++ and Python3 will be available in the contest system.


Each contestant will receive the official English version of tasks on each contest day. For those contestants who requested the translation of the tasks, an additional version of the tasks in the requested language will also be provided. Each contestant will have online access to the official English version of tasks and all task translations in electronic format (PDF).

On each competition day, contestants will be given four tasks to solve in 5 hours. The tasks will be in random order, that is tasks are not sorted by difficulty. The task will be sorted by difficulty as perceived by the scientific committee. Note that contestants might disagree with the order so we suggest that they read all the problems. Remember that hard problems can have easy subtasks.

The Jury guarantees that there are C++17 solutions to every task which fit within the specified memory and time limits by a generous margin. It is also guaranteed that every task is fully solvable in Python3, even though this solution might be more involved and closer to the time and memory limits (e.g. recursion might be too slow).

If the contestants are participating from an online hub organised by their country, it is the responsibility of the hub organisers to arrange for printing of the task statements as needed.


In the competition site, the contestants will be provided with blank paper and writing tools. The contestants can ask for more in case they run out. On the competition days, contestants may not bring anything into the competition rooms, except for the following items under the proviso that they cannot transmit or store any data in electronic or printed format (other than the purpose for which they have been designed):

For the case of snacks, the competition site organisers shall provide all contestants with some amount of snacks. In cases when a contestant would still like to bring in snacks, the contestant should make sure that the snacks are neither noisy nor smelly, and are not disturbing for other contestants in any other way. In case of complaints from other contestants during the contest, the snack might be removed.

Any attempts to bring any other items unlisted above into the competition rooms are considered cheating. In particular, the following items are strictly prohibited in the competitions:

The following items must be brought to (and left at) the practice session if the contestant wishes to use them during the competition days:

Any electronic or printed materials provided by the organisers during a competition round may be used by the contestants (e.g., a Users Guide to the Contest System or any electronic documentation or reference manuals provided in the installed contest environment or on the provided grading system).

Assistance and Clarification

Contestants may ask the support staff for assistance at any time. Contestants may use the system to call for the support staff for task related issues, and ask the room supervisor in case of technical difficulties.

During the competition, contestants may submit Assistance and Clarification Requests concerning competition tasks, rules, and/or grading. Contestants may submit Assistance and Clarification Requests by using the grading system. Contestants will receive a reply from the Scientific Committee via the grading system.

Questions may be expressed either in the contestant’s preferred language or in English. If applicable, delegation leaders will translate the questions into English after they are submitted and before they are sent to the Scientific Committee. The Scientific Committee will respond to every question submitted by the contestants during the competition. Since this might take some time, contestants should continue working while waiting for an answer to their questions.

Contestants should phrase their task-related questions so that a yes/no answer will have a clear meaning. Contestants should not ask negative questions such as “Isn’t it true that…?” because the yes/no answer to such questions may cause confusion depending on the native language of the contestants. Instead, positive questions of the form “Is it true that…?” are recommended.

Contestants are free to phrase their technical or contest related issues in any form. These issues/questions should not be related to tasks at all. Such questions will be fully clarified.

Grading System

EGOI 2023 will use Kattis as the grading system. Login details to the grading system will be given out on each competition day.

Contestants will be able to see the score of their own submissions on the grading system, but not a scoreboard or their overall rank.


Contestants must submit their solutions for tasks by using the grading system. The submission rate of each contestant is limited. A contestant can submit a solution only if they have submitted less than 15 solutions during the last 15 minutes. However, you can always submit 60 seconds after your last submission.

There is no restriction on the number of times a program may be edited, compiled, and run on the contestants’ computers.

Each submitted source program must be written in C++17 or Python3, the source code file must be smaller than 128 KB and the evaluation server must be able to compile it in less than 30 seconds while using at most 512 MiB of memory. The versions and compilation procedures used by the grading system can be found at the following links: C++ and Python3; note that they differ a bit to the versions installed at the contestant’s computers.

The contestants submit their solutions via the grading system and can use the system to view the status of their submissions. When a solution is submitted, it will be compiled and graded. After this, the contestant can view the score achieved by their submission. Each submission will be graded on several test cases.

The possible judgements are (for more details, see Kattis Judgements):

Test cases are grouped into subtasks, each worth some points. The grading system will show the score of each subtask and the outcome of the first non-Accepted test cases in each subtask, if such a case exists. However, input and output data are not shown to the contestant.

A subtask is solved if every test in it is solved correctly and within time and memory limits. A submission will receive points for all subtasks that it solves.


The contestants will see their final score for each task in the contest system. However, there is a small chance that the score will change later due to appeals: submissions may be re-graded, and the final score will be that yielded by the last grading.

Each task is worth a total of 100 points if solved fully, and partial credit will be given as specified in the task statements.

Tasks might be divided into several subtasks, each worth a portion of the total points. Other tasks might use a different way of calculating the score; if so this will be specified in the task statement.

The contestant’s score on a problem is the maximum score over all their submissions on the problem. For example, say the first subtask is solved in one submission and the second subtask in another, then the contestant might not get the points for both of these subtasks. In order to receive the points for both subtasks, the contestant should submit a single solution solving both of them to the grading system.

The End of the Competition

The remaining time of the competition will be displayed in the grading system. Should a contest extension occur, it will be announced in the grading system in the form of a notification. At the end of the competition, the grading system will stop receiving submissions and the contestants must stop using the computer immediately and remain seated until instructed otherwise. For online delegations, the virtual machines must be kept running in full-screen mode until the Technical Committee authorises their shutdown.


Contestants must use only the virtual machine and account assigned to them on each competition day. In particular:

All of the above actions are considered cheating, and may result in disqualification.

Appeal Process

Submitted solutions are evaluated using data which conform to the specification given in the problem statement, but which are hidden from contestants during the competition.

Provisional grades, based on these tests, are available immediately to contestants. In the event of an error with the test data, the Scientific Committee will attempt to, but is not obligated to follow the following process:

This hidden data will be made available electronically in the competition area during the scheduled time for analysis after each competition. Contestants and team leaders may use the contestant’s workstations to verify that the grades are assessed correctly.

A Team Leader may file an appeal by completing an Appeal Form and submitting it to the Scientific Committee at least 30 minutes prior to the final GA meeting of that competition day. The GA will be informed of where Appeal Forms can be collected, and where they can submit them to the Scientific Committee. Every appeal will be reviewed by the Scientific Committee and the team leader will be notified of the committee’s decision. All appeals and their disposition will be summarised at the final GA meeting of that competition day. In the event that every submission of a task should be re-graded and re-scored as a consequence of an accepted appeal, note that re-scoring may result in a higher or lower score for any contestant. Should anyone’s score change after grading results have been published, the new results will be published again. Score changes resulting from this are not appealable.

Proctoring - for online delegations only

Due to travel distance, some countries will take part in EGOI 2023 online. To maintain the integrity of the competition, the host asks the teams to assist in enforcing the competition rules. The following proctoring rules are introduced.

Each competition site, regardless of the number of participants, requires at least two proctors, whose role is to ensure that the contest rules are observed and a fair competition is held. This includes, but is not limited to:

The proctors should organise a suitable competition area and provide the contestants with appropriate supplies (writing papers, printing, snacks …). They are expected to be the first point of contact for the contestants for any technical issues. The proctors will also be in contact with the organising committee to ensure that the contest starts and ends according to the schedule and relay any important announcements. It is highly encouraged to organise a joint competition site for all the participants of a single country.

At least one of the proctors must be present physically at the contest site. This proctor should not have any conflict of interest with the performance of the participant, e.g. contestant’s relatives or the main coach of the contestant.

The General Assembly members who participate in any of the translation sessions must not communicate with the contestants prior to the contest start. Therefore, each site requires at least one proctor to help with the setup who did not participate in the translation session.

Screen Recording - for online delegations only

We require delegations participating online to record their contestants screens with the feature provided in the VM. Note that screen recording does not start automatically so teams participating remotely will need to run these commands manually before and after the contest.

Screen recording is available in the contest VM and can be started by running egoi recording start from a terminal. You can then run egoi recording status to verify that screen recording has started successfully, and egoi recording stop to stop and upload the recording.