\prologcode{./src/hs.pl}
\end{listing}
-\tikzstyle{level 1}=[level distance=1cm, sibling distance=1cm]
-\tikzstyle{level 2}=[level distance=1cm, sibling distance=1cm]
-\tikzstyle{bag} = [text width=4em, text centered]
-\tikzstyle{end} = [minimum width=3pt, inner sep=0pt]
\begin{figure}[H]
\caption{Examples of good hitting set trees}
\begin{tikzpicture} [grow=down]