euler.tex

\documentclass{standalone}
\usepackage{tikz}

\begin{document}
\begin{tikzpicture}
\draw[rounded corners=2mm,->,thick,>=stealth] (0,0) -- (2,0) -- (0,2) -- (2,2) -- (0,0) -- (0,2) -- (1,3) -- (2,2) -- (2,0);
\begin{scope}[xshift=3cm]
\node[circle,draw] (00) at (0,0) {3};
\node[circle,draw] (20) at (2,0) {3};
\node[circle,draw] (02) at (0,2) {4};
\node[circle,draw] (22) at (2,2) {4};
\node[circle,draw] (13) at (1,3) {2};
\draw (00) edge (20) edge (02) edge (22);
\draw (02) edge (22) edge (20);
\draw (13) edge (02) edge (22);
\draw (22) edge (20);
\end{scope}
\end{tikzpicture}
\end{document}