Problem Package Format

This is the legacy-icpc version of the Kattis problem package format. It is also known as the ICPC subset.

Overview

This document describes the format of a Kattis problem package, used for distributing and sharing problems for algorithmic programming contests as well as educational use.

General Requirements

The package consists of a single directory containing files as described below. The name of the directory must consist solely of lower case letters a-z and digits 0-9. Alternatively it can be a ZIP compressed archive of such a directory with identical base name and extension .kpp or .zip.

All file names for files included in the package must match the following regexp:

[a-zA-Z0-9][a-zA-Z0-9_.-]*[a-zA-Z0-9]

I.e., it must be of length at least 2, consist solely of lower or upper case letters a-z, A-Z, digits 0-9, period, dash or underscore, but must not begin or end with period, dash or underscore.

All text files for a problem must be UTF-8 encoded and not have a byte order mark.

All floating point numbers must be given as the external character sequences defined by IEEE 754-2008 and may use up to double precision.

Programs

There are a number of different kinds of programs that may be provided in the problem package; submissions, input validators, output validators. All programs are always represented by a single file or directory. In other words, if a program consists of several files, these must be provided in a single directory. The name of the program, for the purpose of referring to it within the package is the base name of the file or the name of the directory. There can't be two programs of the same kind with the same name.

Validators and graders, but not submissions, in the form of a directory may include two POSIX-compliant scripts "build" and "run". If at least one of these two files is included:

1. First, if the build script is present, it will be run. The working directory will be (a copy of) the program directory. The run file must exist after build is done.
2. Then, the run file (which now exists) must be executable, and will be invoked in the same way as a single file program.

Programs without build and run scripts are built and run according to what language is used. Language is determined by looking at the file endings. If a single language from the table below can't be determined, building fails. In the case of Python 2 and 3 which share the same file ending, language will be determined by looking at the shebang line which must match the regular expressions in the table below.

For languages where there could be several entry points, the default entry point in the table below will be used.

Problem Metadata

Metadata about the problem (e.g., source, license, limits) are provided in a UTF-8 encoded YAML file named problem.yaml placed in the root directory of the package.

The keys are defined as below. Keys are optional unless explicitly stated. Any unknown keys should be treated as an error.

License

Allowed values for license.

Values other than unknown or public domain requires rights_owner to have a value.

Limits

A map with the following keys:

For most keys the system default will be used if nothing is specified. This can vary, but you SHOULD assume that it's reasonable. Only specify limits when the problem needs a specific limit, but do specify limits even if the "typical system default" is what is needed.

Problem Statements

The problem statement of the problem is provided in the directory problem_statement/.

This directory must contain one file per language, for at least one language, named problem.<language>.<filetype>, that contains the problem text itself, including input and output specifications, but not sample input and output. Language must be given as the shortest ISO 639 code. If needed a hyphen and a ISO 3166-1 alpha-2 code may be appended to ISO 639 code. Optionally, the language code can be left out, the default is then English (en). Filetype can be either tex for LaTeX files, or pdf for PDF.

Please note that many kinds of transformations on the problem statements, such as conversion to HTML or styling to fit in a single document containing many problems will not be possible for PDF problem statements, so using this format should be avoided if at all possible.

Auxiliary files needed by the problem statement files must all be in <short_name>/problem_statement/. problem.<language>.<filetype> should reference auxiliary files as if the working directory is <short_name>/problem_statement/. Image file formats supported are .png, .jpg, .jpeg, and .pdf.

A LaTeX file may include the Problem name using the LaTeX command \problemname in case LaTeX formatting of the title is wanted.

The problem statements must only contain the actual problem statement, no sample data.

Attachments

Public, i.e. non-secret, files to be made available in addition to the problem statement and sample test data are provided in the directory attachments/.

Test data

The test data are provided in subdirectories of data/. The sample data in data/sample/ and the secret data in data/secret/.

All input and answer files have the filename extension .in and .ans respectively.

Annotations

One hint, description, and/or illustration file may be provided per test case. The files must share the base name of the associated test case. Description and illustration files are meant to be privileged information.

• A hint provides feedback for solving a test case to, e.g., somebody whose submission didn't pass.

• A description conveys the purpose of a test case. It is an explanation of what aspect or edge case of the solution that the input file is meant to test.

• An illustration provides a visualization of the associated test case. Note that at most one image file may exist for each test case.

Interactive Problems

For interactive problems, any sample test cases must provide an interaction protocol with the extension .interaction for each sample demonstrating the communication between the submission and the output validator, meant to be displayed in the problem statement. An interaction protocol consists of a series of lines starting with > and <. Lines starting with > signify an output from the submission to the output validator, while < signify an input from the output validator to the submission.

A sample test case may have just an .interaction file without a corresponding .in and .ans file. However, if either of a .in or a .ans file is present the other one must also be present. Unlike .in and .ans files for non-interactive problem, interactive .in and .ans files must not be displayed to teams: not in the problem statement, nor as part of sample input download. If you want to provide files related to interactive problems (such as testing tools or input files) you can use attachments.

Test Data Groups

At the top level, the test data is divided into exactly two groups: sample and secret.

Test files and groups will be used in lexicographical order on file base name. If a specific order is desired a numbered prefix such as 00, 01, 02, 03, and so on, can be used.

Example Submissions

Correct and incorrect solutions to the problem are provided in subdirectories of submissions/. The possible subdirectories are:

Every file or directory in these directories represents a separate solution. Same requirements as for submissions with regards to filenames. It is mandatory to provide at least one accepted solution.

Submissions must read input data from standard input, and write output to standard output.

Input Validators

Input Validators, for verifying the correctness of the input files, are provided in input_validators/ (or the deprecated input_format_validators/). Input validators can be specified as VIVA-files (with file ending .viva), Checktestdata-file (with file ending .ctd), or as a program.

All input validators provided will be run on every input file. Validation fails if any validator fails.

Invocation

An input validator program must be an application (executable or interpreted) capable of being invoked with a command line call.

All input validators provided will be run on every test data file using the arguments specified for the test data group they are part of. Validation fails if any validator fails.

When invoked the input validator will get the input file on stdin.

The validator should be possible to use as follows on the command line:

./validator [arguments] < inputfile

Output

The input validator may output debug information on stdout and stderr. This information may be displayed to the user upon invocation of the validator.

Exit codes

The input validator must exit with code 42 on successful validation. Any other exit code means that the input file could not be confirmed as valid.

Dependencies

The validator MUST NOT read any files outside those defined in the Invocation section. Its result MUST depend only on these files and the arguments.

Output Validators

Overview

An output validator is a program that is given the output of a submitted program, together with the corresponding input file, and a correct answer file for the input, and then decides whether the output provided is a correct output for the given input file.

A validator program must be an application (executable or interpreted) capable of being invoked with a command line call. The details of this invocation are described below. The validator program has two ways of reporting back the results of validating:

1. The validator must give a judgement (see Reporting a judgement).
2. The validator may give additional feedback, e.g., an explanation of the judgement to humans (see Reporting Additional Feedback).

Custom output Validators are used if the problem requires more complicated output validation than what is provided by the default diff variant described below. They are provided in output_validators/, and must adhere to the Output validator specification.

All output validators provided will be run on the output for every test data file using the arguments specified for the test data group they are part of. Validation fails if any validator fails.

Default Output Validator Specification

The default output validator is essentially a beefed-up diff. In its default mode, it tokenizes the files to compare and compares them token by token. It supports the following command-line arguments to control how tokens are compared.

When supplying both a relative and an absolute tolerance, the semantics are that a token is accepted if it is within either of the two tolerances. When a floating-point tolerance has been set, any valid formatting of floating point numbers is accepted for floating point tokens. So for instance if a token in the answer file says 0.0314, a token of 3.14000000e-2 in the output file would be accepted. If no floating point tolerance has been set, floating point tokens are treated just like any other token and has to match exactly.

Invocation

When invoked the output validator will be passed at least three command line parameters and the output stream to validate on stdin.

The validator should be possible to use as follows on the command line:

./validator input judge_answer feedback_dir [additional_arguments] < team_output [ > team_input ]

The meaning of the parameters listed above are:

• input: a string specifying the name of the input data file which was used to test the program whose results are being validated.

• judge_answer: a string specifying the name of an arbitrary "answer file" which acts as input to the validator program. The answer file may, but is not necessarily required to, contain the "correct answer" for the problem. For example, it might contain the output which was produced by a judge's solution for the problem when run with input file as input. Alternatively, the "answer file" might contain information, in arbitrary format, which instructs the validator in some way about how to accomplish its task. The meaning of the contents of the answer file is not defined by this format.

• feedback_dir: a string which specifies the name of a "feedback directory" in which the validator can produce "feedback files" in order to report additional information on the validation of the output file. The feedbackdir must end with a path separator (typically ‘/' or ‘\' depending on operating system), so that simply appending a filename to feedbackdir gives the path to a file in the feedback directory.

• additional_arguments: in case the problem specifies additional validator_flags, these are passed as additional arguments to the validator on the command line.

• team_output: the output produced by the program being validated is given on the validator's standard input pipe.

• team_input: when running the validator in interactive mode everything written on the validator's standard output pipe is given to the program being validated. Please note that when running interactive the program will only receive the output produced by the validator and will not have direct access to the input file.

The two files pointed to by input and judge_answer must exist (though they are allowed to be empty) and the validator program must be allowed to open them for reading. The directory pointed to by feedback_dir must also exist.

Reporting a judgement

A validator program is required to report its judgement by exiting with specific exit codes:

• If the output is a correct output for the input file (i.e., the submission that produced the output is to be Accepted), the validator exits with exit code 42.
• If the output is incorrect (i.e., the submission that produced the output is to be judged as Wrong Answer), the validator exits with exit code 43.

Any other exit code (including 0!) indicates that the validator did not operate properly, and the judging system invoking the validator must take measures to report this to contest personnel. The purpose of these somewhat exotic exit codes is to avoid conflict with other exit codes that results when the validator crashes. For instance, if the validator is written in Java, any unhandled exception results in the program crashing with an exit code of 1, making it unsuitable to assign a judgement meaning to this exit code.

Reporting Additional Feedback

The purpose of the feedback directory is to allow the validator program to report more information to the judging system than just the accept/reject verdict. Using the feedback directory is optional for a validator program, so if one just wants to write a bare-bones minimal validator, it can be ignored.

The validator is free to create different files in the feedback directory, in order to provide different kinds of information to the judging system, in a simple but organized way. For instance, there may be a "judgemessage.txt" file, the contents of which gives a message that is presented to a judge reviewing the current submission (typically used to help the judge verify why the submission was judged as incorrect, by specifying exactly what was wrong with its output). Other examples of files that may be useful in some contexts (though not in the ICPC) are a score.txt file, giving the submission a score based on other factors than correctness, or a teammessage.txt file, giving a message to the team that submitted the solution, providing additional feedback on the submission.

A judging system that implements this format must support the judgemessage.txt file described above (I.e., content of the "judgemessage.txt" file, if produced by the validator, must be provided by the judging system to a human judge examining the submission). Having the judging system support other files is optional.

Note that a validator may choose to ignore the feedback directory entirely. In particular, the judging system must not assume that the validator program creates any files there at all.

Examples

An example of a judgemessage.txt file:

Team failed at test case 14.
Team output: "31", Judge answer: "30".
Team failed at test case 18.
Team output: "hovercraft", Judge answer: "7".
Summary: 2 test cases failed.

An example of a teammessage.txt file:

Almost all test cases failed, are you even trying to solve the problem?

Validator standard output and standard error

A validator program is allowed to write any kind of debug information to its standard error pipe. This information may be displayed to the user upon invocation of the validator.