rbxTeX statements#

rbxTeX (extension: .rbx.tex) is the recommended format for writing problem statements in rbx. It is a superset of LaTeX that adds a structured, block-based approach to writing statements, making them easier to organize and maintain.

Why rbxTeX?#

Standard LaTeX files can be cluttered with boilerplate code (document headers, packages, macros). rbxTeX helps separating the content of the problem (description, input, output) from the layout (the LaTeX template) with the use of the templating engine Jinja2.

Key features:

Block-based: Organize content into logical sections (legend, input, etc.).
Variable interpolation: Use \VAR{...} to inject dynamic values like time limits and other user-defined variables.
Sample generation: Samples are automatically fetched and made accessible as a Jinja2 variable.
Leverage full LaTeX power: You can still use any LaTeX capability, rbxTeX is just a wrapper around LaTeX.

Definition#

rbxTeX statements usually consist of two files: the main file (usually named statement.rbx.tex) and the template file (usually named template.rbx.tex).

The main file contains the blocks that define the content of the problem statement. Think of it as usually containing a few sections, such as the legend, the input, the output, the notes, etc.

The template file contains the layout of the problem statement, and through the use of Jinja2, it can access the content of the blocks defined in the main file and render them in the appropriate place.

In a problem, a rbxTeX statement can be defined as:

problem.rbx.yml

statements:
  - name: statement
    path: statement/statement.rbx.tex # The main file
    configure:
      - type: rbx-tex
        template: "statement/template.rbx.tex" # The template file

For contest-level statements, please read the Contest Statement section.

Syntax#

rbxTeX introduces a few special commands on top of LaTeX.

Blocks#

Blocks are the core of rbxTeX statement organization that are usually placed in the main file. In rbxTeX, instead of mixing your content with layout commands (like \section or \begin{itemize}), you define semantic blocks of content. The template then decides where and how to render these blocks.

This separation of concerns allows you to:

Change the look of your statement just by swapping the template, without touching the content.
Reuse content easily (e.g., using the same block for both the full statement and a simplified statement).

statement.rbx.tex

%- block input
The input consists of a single integer $N$.
%- endblock

%- block output
The output consists of a single integer $N$.
%- endblock

You don't always need to define custom blocks, rbx works out-of-the-box with a few pre-defined blocks that adhere to the nomenclature and sectioning used by Polygon. See the default blocks section for more information.

Variables#

You can inject variables from problem.rbx.yml using the \VAR{<variable-name>} syntax, or \VAR{vars.<variable-name>} syntax when there's a conflict between built-in variables and your custom variables.

statement.rbx.texproblem.rbx.yml

statement.rbx.tex

%- block input
The input consists of a single integer $N$
($\VAR{N.min} \le N \le \VAR{N.max}$).
%- endblock

problem.rbx.yml

vars:
  N:
    min: 1
    max: 100

Comments#

You can use standard LaTeX comments % ..., but rbxTeX also supports block comments that are stripped before processing:

%# This is a comment that won't appear in the final LaTeX output

Other Jinja2 features#

Take a look at Jinja2 website to see how other features work, such as conditionals, loops, etc. These are very powerful for templating.

Default blocks#

The default template supports the following blocks:

Block Name	Description
`legend`	The main problem description (the story and the task).
`input`	Description of the input format.
`output`	Description of the output format.
`interaction`	(Interactive problems only) Description of the interaction protocol.
`notes`	Any additional notes, hints, or explanations.
`editorial`	(Optional) Solution tutorial/editorial.
`explanation_N`	Explanation for the N-th sample (0-indexed).

These can be specified in the main file, and will be rendered in the default templates supported by rbx. It is a good practice to reuse these commonly defined blocks in your own templates as well, since they're semantically meaningful, and have a special treatment for Polygon packages.

Example#

Here is a barebones example of a problem statement written in rbxTeX.

Main (statement.rbx.tex)Template (template.rbx.tex)

%- block description
Alice and Bob are playing a game with a sequence of integers.
The game consists of $K$ turns. In each turn, a player can...

Calculate the final score of the winner.
%- endblock

%- block input
The first line contains two integers $N$ and $K$ ($\VAR{N.min} \le N, K \le \VAR{N.max}$) — the length of the sequence and the number of turns.

The second line contains $N$ integers $A_1, A_2, \dots, A_N$ ($|A_i| \le \VAR{A.max}$).
%- endblock

%- block output
Output a single integer — the final score of the winner.
%- endblock

%- block notes
In the first sample, Alice chooses to...
%- endblock

%# We can explain specific samples using explanation blocks instead of notes if preferred.
%- block explanation_0
This explanation corresponds to the first sample case.
%- endblock

\documentclass{article}
\begin{document}

\section*{\VAR{problem.short_name}. \VAR{problem.title}}

\VAR{problem.blocks.description}

\subsection*{Input}
\VAR{problem.blocks.input}

\subsection*{Output}
\VAR{problem.blocks.output}

\subsection*{Samples}
%- for sample in problem.samples
\subsection*{Sample \VAR{loop.index}}
\begin{itemize}
    \item \textbf{Input:} \texttt{\VAR{sample.inputPath.read_text()}}
    \item \textbf{Output:} \texttt{\VAR{sample.outputPath.read_text()}}
\end{itemize}
%- endfor

%- if problem.blocks.notes is defined
\subsection*{Note}
\VAR{problem.blocks.notes}
%- endif

\end{document}

Learn more about templating#

Learn more about creating your own template in our templating guide.