答案1
您的问题类似于这。我已获取用户的代码@sergej我还做了一些改变:
\documentclass[tikz,border=10pt]{standalone}
\usetikzlibrary{arrows,automata}
\begin{document}
\begin{tikzpicture}[node distance=2.3cm,->,>=stealth',auto,
every edge/.append style={thick}]
\node[state] (1) {$A$};
\node[state] (2) [right of=1] {$R$};
\path (1) edge[loop left] node{$S_1$} (1)
edge[bend left] node{$\scriptstyle S_2$} (2)
(2) edge[loop right] node{$S_4$} (2)
edge[bend left] node{$\scriptstyle S_3$} (1);
\end{tikzpicture}
\end{document}