Is there any easy way to make this directed graph?
\begin{tikzpicture}[x=2cm, y=2cm]
\tikzstyle{every node}=[draw, circle, fill=white, inner sep=3pt,minimum size=18pt]
\draw (0,0) node(IN){IN} -- (1,0) node(1){1} -- (2,0.5) node(2){2} -- (3,0) node(OUT){OUT};
\draw (IN) -- (1) -- (2,-0.5) node(3){3} -- (OUT);
\end{tikzpicture}