How to Write Pseudocode in Markdown and Export It to PDF

Markdown does not define a standard algorithm or pseudocode block. A fenced code block is the simplest portable choice, but it will usually appear as monospaced text rather than a numbered, captioned algorithm. If you are producing a PDF with Pandoc and want that structured layout, use LaTeX’s algorithm and algpseudocode packages inside a raw LaTeX block.

Option 1: Use a fenced code block

For notes, drafts, or content that needs to display in several Markdown renderers, write pseudocode as ordinary text inside a fence:

BinarySearch(A, x):
    low = 0
    high = length(A) - 1
    while low <= high:
        mid = floor((low + high) / 2)
        if A[mid] = x:
            return mid
        if A[mid] < x:
            low = mid + 1
        else:
            high = mid - 1
    return -1

The text label avoids asking Pandoc to apply the syntax rules of a programming language. The fence preserves indentation and makes the pseudocode easy to read, but does not add an algorithm number, caption, or automatically formatted line numbers. Markdown renderers vary in their support for syntax highlighting, so do not rely on highlighting for meaning.

Option 2: Use a LaTeX algorithm environment in Pandoc

For a PDF with a caption and line numbers, save a file such as pseudocode.md with a YAML header, then put the algorithm in a raw LaTeX block. This complete example uses zero-based indexing and assumes A is sorted in ascending order.

---
title: Binary search pseudocode
header-includes:
  - |
    \usepackage{algorithm}
    \usepackage{algpseudocode}
---

```{=latex}
\begin{algorithm}
\caption{Binary search}
\begin{algorithmic}[1]
\Procedure{BinarySearch}{$A, x$}
    \State $low \gets 0$
    \State $high \gets |A| - 1$
    \While{$low \le high$}
        \State $mid \gets \lfloor (low + high)/2 \rfloor$
        \If{$A[mid] = x$}
            \State \Return $mid$
        \ElsIf{$A[mid] < x$}
            \State $low \gets mid + 1$
        \Else
            \State $high \gets mid - 1$
        \EndIf
    \EndWhile
    \State \Return $-1$
\EndProcedure
\end{algorithmic}
\end{algorithm}
```

Convert it to PDF with Pandoc and a LaTeX engine installed:

pandoc pseudocode.md --pdf-engine=xelatex -o pseudocode.pdf

algorithm provides the floating algorithm environment and caption; algpseudocode provides commands such as \Procedure, \State, \While, and \If. The optional [1] on algorithmic requests line numbers. The {=latex} fence tells Pandoc to pass the enclosed LaTeX through rather than treat it as ordinary code. The packages must be installed in the LaTeX distribution used by the chosen engine.

The search returns the index of x if it is present, and -1 otherwise. Each loop iteration halves the remaining search interval, so the running time is $O(\log n)$ for an array of length $n$; the extra space is $O(1)$.

Choosing between the two formats

Need	Suitable format
A readable, portable snippet	Fenced Markdown code block
Captions, algorithm numbering, or line numbers in PDF	LaTeX algorithm environment
The same source rendered to HTML and PDF	Fenced code, or separate output-specific formatting

Raw LaTeX is specific to LaTeX-based output. It can work well for Pandoc-to-PDF, but a renderer targeting HTML may omit it or show it as text. If you need both outputs, test each target and consider keeping a plain pseudocode version for HTML.

Common mistakes

• Expecting Markdown to format an algorithm automatically. A code fence preserves text formatting; it does not create a captioned algorithm float.
• Leaving out the LaTeX packages. Commands such as \Procedure are not built into Pandoc. Add the package that defines them and make sure it is installed.
• Using a regular code fence for LaTeX. A fence such as ```latex displays the source as code. Use the {=latex} raw block when the goal is to execute LaTeX during PDF generation.
• Assuming a float stays exactly where it appears. LaTeX may move an algorithm to improve page layout. If its position matters, look up the float-placement options supported by your chosen packages rather than assuming Markdown controls it.
• Forgetting the PDF engine. Pandoc needs a working LaTeX installation to create PDFs this way. If conversion fails, check that the engine and required packages are installed before changing the pseudocode.