Task Types

All of the tasks in CEOI 2011 are designed to be of algorithmic nature. Tasks may be of the following types:

  • Batch tasks: Solutions comprise a single source file of a computer program which reads data from standard input and writes its answer to standard output.
  • Reactive tasks: Solutions comprise a single source file of a computer program which interacts with an “opponent” program provided by the organizers. The reactive interface may be implemented either by using standard input/output, or by linking modules provided by the contestant and the organizers.
  • Output-only tasks: The contestants are given input files and they have to produce correct output files by any means available.


As usual, for every task other than output-only tasks, the following limits will be enforced on the contestants’ submissions:

  • Time limit: a limit on the total processor time the process may consume while solving a given input.
  • Memory limit: a limit on the total amount of memory the process may have allocated at any moment. Note that this limit includes not only the variables, but also the executable code, global data, the stack, etc. There is no separate limit on the stack size.
  • Source size limit: no submitted program may exceed 100 kB in size. The size of the compiled program must not exceed 5 MB. Maximum compilation time is 30 seconds.

All task dependent limits will be announced in the problem statements.

Competition Equipment and Environment

The contestants’ machines will run a specially prepared Linux distribution.

Compiler versions that will be used:

  • fpc ≥ 2.2.2,compilation command (for the program abc.p): ppc386 -O2 -XS -Xt abc.p
  • gcc ≥ 4.4.1,compilation command (for the program abc.c or abc.cpp): gcc -O2 -static abc.c -lm or g++ -O2 -static abc.cpp -lm

To compile the program abc.c | abc.cpp | abc.p on a contestant’s computer using the aforementioned compilation instructions, simply write make abc. As a result, the binary file abc will be created.


Installed software will include:

  • editors: mcedit, vi/vim, emacs, kwrite, gedit, gvim,
  • IDEs: codeblocks, geany, lazarus
  • other commands available: mc, gdb,
  • STL and Free Pascal documentation.

Submitting Solutions

The contestants’ submissions will be evaluated by a competition server. Each contestant will be assigned a username and a password for accessing the server. The environment on the server will be as close as possible to the environment on the contestants’ machines, although the hardware can be different. The contestants will be able to run their solutions on the server using test facility.

Contestants submit solutions to the competition server via a web browser. Solutions for tasks may be submitted at any time during the contest.

For tasks which require output files as solutions, contestants must submit a zip file containing all produced output files. A more detailed explanation will be provided in the task’s description.

For tasks which require programs as solutions, the submission facility will accept C, C++ or Pascal programs, verify that the program compiles and obeys the stated limits on program source size and compile time; the submission facility will then run the program on the sample test cases given in the task description, enforcing the relevant run-time resource constraints.

Grading information will be reported back to the contestant for ech test case.

For each task, the best accepted submission for that task will be used to award points.

For each task at most 12 submisssion allowed.


For each task the test data will be divided into batches, with each batch containing one or more test inputs. A test input is solved correctly if the submitted program produces a correct output file within the enforced limits. For output-only tasks test input is solved correctly if the corresponding output file submitted by the contestant is correct. A batch is solved correctly if each of the inputs it contains is solved correctly. Points are awarded only for correctly solved batches of inputs.

Clarification Requests

During the first two hours of competition, contestants may submit written questions concerning any ambiguities or items needing clarification in the competition tasks. Questions must be submitted via the competition server, expressed either in the contestant’s native language or in English. If required, delegation leaders will translate their contestants’ 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. Contestants should phrase their questions so that a yes/no answer will be meaningful. Questions will be answered with one of the following:

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