European Junior Olympiad in Informatics 2026

Kaunas, Lithuania · July 24–30, 2026

Contest Rules

1. Preambles

This document may be revised to address omissions or inconsistencies, but it will not undergo substantial changes.

Delegation Leaders are responsible for ensuring that all members of their delegation fully understand these rules and comply with them.

For additional documents regulating EJOI, please refer to:

2. Contest schedule

There are two contest days. On each day, contestants are given three tasks to be solved in 4 hours.

A 2-hour Practice Contest is held before the first contest day to familiarize all contestants with their workstations and the grading system. The tasks used in the Practice Contest are published before the EJOI.

3. Grading system

Grading and evaluation take place on the grading system, which provides a similar execution environment for every submitted solution.

The workstations have network access to the grading system.

Grading is performed in an environment that differs from the one available on the contestant workstations. Contestants can use the “Testing” section in the CMS (Contest Management System, which is available in the contestant workstations) to run their programs in the official grading environment.

4. Tasks

Each contestant will receive the official English version of the tasks in an envelope on each contest day. The team leaders may translate the task statements for contestants, and the translated statements will be provided in the envelope with the English version. Each contestant will have online access to the official English version of the task statements and all translations in electronic format (PDF).

Each task is either a programming task (the solution is source code) or an output-only task (the solution is a set of output files). Each task is divided into a number of subtasks, each worth a portion of the total points.

For each programming task, time and memory limits are specified. In general, time and memory limits are generous (for example, double those required by the expected solution). The memory limit is on the overall memory usage, including executable code size, stack, dynamically allocated memory, etc.

For each task, the contestants can download a zip file from the grading system. For programming tasks, the file contains interface files, a sample grading program, an example implementation of the required source file, and the input and output files of the examples in the task statement. The provided example implementation demonstrates the interface of the task but does not solve the task. The sample grader provided on the workstation is not the same as the official grader used by the grading system.

5. Solutions and submissions

Contestants submit their solutions for the tasks via the grading system. Unless otherwise stated, the following restrictions apply to the submissions:

Using multiple threads is not allowed.

6. Scoring

The scores for each task will be calculated as follows:

For example, consider a contestant who made two submissions on a task that contains two subtasks. If the first submitted solution got 30 points for the first subtask and 10 points for the second subtask, and the second solution got 0 points for the first subtask and 40 points for the second subtask, then the final score for this task will be 70.

The maximum score for each task is 100 points.

7. Feedback

Contestants can use the grading system to view the status of their submissions and get a short report on the compilation results of their source code.

For each submission, the grading system reports the points for each subtask.

Unless otherwise stated, if a subtask is not fully solved, the grading system provides feedback only for the first test case among the lowest scored test cases in the subtask and all tests before that.

The feedback includes the test case number and one of the following verdicts:

A contestant may receive a “Protocol violation” feedback if their program does not follow the correct protocol described in the problem statement.

Some possible reasons include:

However, it should be noted that submissions that exhibit the above behavior may not always result in “Protocol violation” feedback and the list above is also not exhaustive.

Unless otherwise stated, the “Output is partially correct” feedback is displayed when a submission receives a partial score for a test case in a subtask with partial scoring.

The test cases are ordered the same way in all the submissions. No information on the actual test cases, the output produced by the contestant solution, or any other execution details will be given to the contestant.

It should be noted that the scores and points reported in the feedback are only provisional. There are two ways in which they can change after they have been reported to the contestant:

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:

8. Quarantine

To protect task confidentiality, all direct and indirect contacts and communication between contestants and delegation leaders are prohibited from the moment tasks for a contest day are presented to the members of the GA until the end of that contest day. During this time, contestants must not communicate by any means, direct or indirect, with anyone who knows the tasks (except for the usual communication with the Scientific Committee during the contest).

Until the end of each contest day, GA meeting attendees must not share task-related information with anyone who does not know the contest tasks without explicit approval from the Scientific Committee. The contestants, the GA members, and anyone else who has had access to the tasks must obey any instructions which restrict their access to specific parts of the EJOI venue.

If a contestant violates the quarantine, the contestant may be subject to disqualification. If some other person associated with a national delegation violates the quarantine, then all contestants of that delegation may be subject to disqualification.

9. Supplies

9.1. Provided items

In the contest room, the following items will be provided:

Any electronic or printed materials provided by the organizers during a contest round may be used by the contestants (e.g., any electronic documentation or reference manuals provided in the installed Contest Equipment or on the provided grading system).

9.2. Permitted items

On the contest days, contestants may bring the following items into the contest room:

9.3. Permitted items with approval

Contestants may request to use additional items, provided that these items cannot transmit or store any data in electronic, printed, or other written format (other than their designed purpose). The following items are examples of items that may be requested:

Bringing these additional items requires prior approval from the Technical Committee. A contestant must submit these items by leaving them in a designated location provided by the Technical Committee on their workstation during the Practice Contest.

As soon as the Practice Contest is over, the Technical Committee will check the submitted items. If there are rejected items, the delegation leader of the contestant will be notified, and they are allowed to resubmit replacements. The approved items will be kept by the Technical Committee and given to the contestants at the start of each contest day. However, during the contest, the Technical Committee may decide to remove any of these approved items if they deem that the item’s usage is disruptive to other contestants during the contest.

In emergency situations, last-minute item submission at the competition checkpoint before each competition day is allowed. Any item presented, other than those explicitly approved (ID badge, clothing, and jewelry), must undergo an immediate review by a committee member. Any item requiring non-trivial technical inspection, including all keyboards and mice, shall be rejected without consideration. Note that the committees cannot guarantee the acceptance of items that would otherwise be permitted under the standard submission procedure.

After the first contest day is over, a contestant must leave the submitted items in the same designated container provided by the Technical Committee on their workstation if they want to continue using these items on the second contest day. Contestants are allowed to submit new items or replacements during the time of analysis for the first contest day, to use them on the second contest day.

At the end of the Practice Contest and the first contest day, any unsubmitted items left on the contestants’ workstations will be cleared and not returned to the workstations. Hence, contestants should take all items with them at the end of the Practice Contest and each contest day.

At the end of the second contest day, contestants should take all the submitted items with them.

Regarding snacks, note that the Organizing Committee will provide all contestants with some number of snacks. In cases when a contestant would still like to bring in snacks, they should make sure that the snacks are not noisy or 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.

9.4. Prohibited items

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

10. Contest

10.1. Starting the contest

All contestants must wear their ID badges during the contest. Each contestant will have a pre-assigned workstation. Contestants should be seated at least 5 minutes before the start of the contest.

Contestants must find their assigned workstation, sit down, and wait for the contest to begin without touching anything (such as keyboards, mice, pens, or paper).

10.2. Clarification requests

During the contest, contestants may ask questions regarding contest tasks, rules, and/or grading. Clarification Requests may be expressed either in English or the contestant’s preferred language. If required, delegation leaders will translate the Clarification Requests into English after they are submitted and before they are processed by the Scientific Committee. The Scientific Committee will respond to every question submitted by the contestants. Since this might take some time, contestants should continue working while waiting for the answer to their questions.

The questions should be submitted using the grading system whenever possible. If this option is not available, either because typing in the contestant’s preferred language is not supported or due to technical issues, contestants can write the question on a printed Clarification Request Form.

Contestants will receive a reply from the Scientific Committee via the grading system, or in writing on the submitted Clarification Request Form.

Questions regarding the contest tasks should be phrased 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.

Questions regarding the contest tasks will be answered with one of the following (if the answer is via the grading system, it will be automatically translated in the selected language of the grading system):

As a general rule, the Scientific Committee only answers “Yes” or “No”, when the corresponding part of the task statement is deemed incorrect, ambiguous, or potentially confusing.

The “No Comment/Please refer to the task statement” answer is commonly given in the following situations:

Additional elaboration of the answer may be provided if the Scientific Committee deems it necessary.

10.3. Assistance requests

Requests not concerning contest tasks, rules, and/or grading would be considered as Assistance Requests. These Assistance Requests should be made by raising a colored card available on the contestant’s desk, depending on the type of request. For any other Assistance Requests, contestants should raise their hand to call the support staff for assistance.

The staff members will deliver Clarification Request Forms, help locate toilets and refreshments, and assist with computer and network problems. They will not answer questions about the contest tasks.

Contestants should not:

10.4. Ending the contest

Two warnings will be given at 15 minutes and 5 minutes before the end of the contest. Each warning will be given by an audible signal. The end of the contest will be announced both verbally and by an audible signal. At the announcement ending the contest, contestants must immediately stop working (unless they request extra time, please see the next paragraph) and wait quietly at their desks without touching the computers or anything on their desks. An additional announcement will be made instructing them to leave their tables and exit the contest room.

If a contestant thinks that they should be given extra time for the contest, they should send a Clarification Request either through the grading system or via a Clarification Request Form as early as possible. They should not leave their desk or talk to other contestants or team leaders after the contest ends and should continue to work. The Scientific Committee will then decide whether to award the extra time, and inform the contestant of the decision as early as possible. If some amount of extra time is granted, all submissions that are made during contest time + extra time would be evaluated.

If the contestant wants to finish the contest earlier, they can leave the contest after informing and receiving permission from staff, but will not be permitted to come back. During the last 15 minutes of each contest it is not allowed to leave.

However, note that the following issues will not be accepted as grounds for requesting extra time:

11. Cheating

Violating any of the following rules is considered cheating and may result in disqualification:

12. Appeal process

The test cases used for grading will be made available in the grading system during the scheduled time for analysis after each competition. Contestants and team leaders may use the contestant’s workstations to verify that the points are given correctly.

A Team Leader may file an appeal by submitting an Appeal Form to the Scientific Committee no later than the later of the following: 60 minutes before the final GA meeting of that competition day, or the end of the planned analysis session of the same competition day. The GA will be informed of where Appeal Forms can be collected, and where they can submit them to the Scientific Committee. All appeals are reviewed by the Scientific Committee, and decisions are communicated to the team leader. All appeals and their resolution will be summarized at the final GA meeting of that competition day.

If every submission of a task should be re-evaluated as a consequence of an accepted appeal, note that re-evaluation may result in a higher or lower points for any contestant. Should anyone’s points change after grading results have been published, new results will be published again. Points changes resulting from this are not appealable.