[Tex/LaTex] Use algorithm2e inside tcolorbox

Question

I use the algorithm2e package to typeset algorithms. Now I would like to put a tcolorbox around an algorithm. My first approach looked like this:

\begin{tcolorbox}
    \begin{algorithm}
        $a \leftarrow 1$
        \caption{My Algorithm}
    \end{algorithm}
\end{tcolorbox}

This yields the following error: LaTeX Error: Not in outer par mode. My understanding is that this happens because both the tcolorbox and the algorithm are floating environments that cannot be nested.

There is already a similar question: How to put \algorithm and \algorithmic environments inside a box? The accepted answer there does not work for me, because it simply describes how to put an arbitrary box around the algorithm. I also tried to use \RestyleAlgo{tcolorbox}, but to no avail. I am looking for a method that specifically uses a tcolorbox.

As a final remark, I do not need to typeset the algorithms particularly with algorithm2e, any other algorithm package will do as well.

Answer 1

The error "Not in outer par mode" is because the algorithm environment wants to float, yet it's contained inside a non-floating tcolorbox. The only way to make algorithm2e not floats its algorithms is to use the [H] float specifier:

\documentclass{article}
\usepackage[paper size={15cm,10cm}]{geometry}
\usepackage[most]{tcolorbox}
\usepackage{algorithm2e}

\begin{document}

\begin{tcolorbox}
  \begin{algorithm}[H]
    $a \leftarrow 1$
    \caption{My Algorithm}
  \end{algorithm}
\end{tcolorbox}
\end{document}