<gh_stars>10-100
\begin{adjustbox}{height=0.4\linewidth}
\begin{tikzpicture}[
  node/.style={
    circle,
    draw=black,
    color=black,
    line width=0.1em,
    minimum size=2.0em,
    inner sep=0em
  }, path/.style={
    line width=0.25em,
    color=Mittel-Blau
  }, level/.style={
    sibling distance = 16.0em/#1,
    level distance = 4.0em
  }, level 3/.style={
    sibling distance = 4.0em,
  }]
\node (0, 0) [node] (root) {12}
child [<-, path] {
  node [node] {7}
  child [<-, path] { node [node] {3} }
  child [->, path] { node [node] {10} }
}
child [->, path] {
  node [node] {18}
  child [<-, path] { node [node] {15} }
  child [->, path] { node [node] {22} }
};
\end{tikzpicture}
\end{adjustbox}