Contest Rules

Noteworthy changes and updates to the 2018 version

Task types

The tasks are designed to be of algorithmic nature. They may be of the following types:

Output-only tasks will not be used in CEOI 2019.


For batch and interactive tasks, the following limits are enforced.

Submitting Solutions

Contestants submit solutions to the contest server via a web-based submission system running on that server.

Solutions for tasks may be submitted at any time during the contest. For each task a contestant may make at most 50 submissions. It is the responsibility of the contestants to submit their solutions to the contest system before the contest is finished. We advise the contestants to reserve enough time before the end of the contest to make sure that all of their solutions are submitted. The contest server shows the official time remaining in the contest.

Submissions are evaluated on identical grading machines. The software environment on grading machines is as close as possible to the environment on the contestant machines.

For tasks which require programs as solutions, the submission facility will accept C++ and Java source files.


Test data for each task will be divided into batches of test inputs that correspond to the subtasks defined in the task statement. A test input is solved correctly if the submitted program produces a correct output file within the enforced limits. A group is solved correctly if each of the inputs it contains is solved correctly.

If a run of a solution returns an exit code other than 0 for any reason, it is judged as Runtime error.

Points are awarded only for correctly solved groups of inputs. If there are special grading rules for the task, the scoring will be clarified within the problem statement.

If a contestant submits more than one solution for the same task, the solution that scored the maximum number of points counts.

Each submission is always tested on all example test cases. The results of these tests have no influence on the scores. In particular, it is possible to fail an example test case and still gain a non-zero score for the task.


Contestants will receive full feedback for every submission. Namely:

Clarification Requests

Contestants may ask the support staff for assistance at any time by raising their hand. This is recommended in case of computer or network problems, requests for additional blank papers, and bathroom breaks. Contestants should not leave their seats until allowed to do so by the support staff.

During the competition, contestants may use the contest server to submit clarification requests. Contestants may use English or their native language. Delegation leaders are responsible for translations between the native language and English.

Task-related questions must be phrased as positive yes/no questions. These questions will be answered with one of the following:

Technical and contest-related questions and comments may be phrased arbitrarily and the Scientific Committee will answer them appropriately. See below for an example.


The Scientific Committee may need to make an announcement during the competition. These announcements will be made in English and they will be both published on the competition server and announced verbally in the contest hall. If a contestant cannot understand the English announcement, they can send a clarification request asking for a translation.

Fair Play

In order to ensure a fair competition, submitted programs are not allowed to:

During the contest, contestants are not allowed to:

All Fair Play limits do apply during the practice session as well. Violation of these rules may be grounds for disqualification.

Competition Supplies

During the contest days, the organizers will provide:

During the practice session and analysis mode, contestants may bring anything they like. During the contest, contestants may only bring the following items:

During the onsite practice session all keyboards, mice, mascots and dictionaries must be submitted to the Technical Committee for approval before they can be installed and used. After the practice session, and again after the analysis session after day 1, these items must remain on the contestant’s desk. After the second competition day, the contestant is responsible for collecting all their belongings.

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:

Appeal Process

During the analysis session after a contest day the secret test data will be made available to the contestants and delegation leaders. Contestants and team leaders may use the contestant workstations to verify that the grading is correct.

A team leader must notify the Scientific Committee about any appeals before the end of an analysis session, and then submit the full text of the appeal in time specified by the Scientific Committee.

Every appeal will be reviewed by the Scientific Committee and the team leader will be notified about the committee’s decision. All appeals and their resolutions will be summarized at a General Assembly meeting.

In the event that a mistake is discovered in the grading of a task, the mistake will be corrected and the submissions of all contestants will be re-graded and re-scored, whether or not the scoring of that particular submission has been appealed. Note that re-scoring may result in a higher or lower score for any contestant.