Drawing an arrow around an automata

Question

Using Tikzpicture, I have the following automata:

\documentclass{article}
\usepackage{tikz}
\begin{document}
\usetikzlibrary{positioning,arrows,automata}
\begin{center}
\begin{tikzpicture}[>=stealth',shorten >=1pt,node distance=2cm,on grid,initial/.style={}]
\node[state,initial]  (a0)                   {};
\node[state]          (a1)  [right =of a0]   {};
\node[state]          (a2)  [right =of a1]   {};
\node[state]          (a3)  [above =of a2]   {};
\node[state]          (a4)  [below =of a0]   {};
\node[state]          (a6)  [right =of a4]   {};
\node[state]          (a7)  [right =of a2]   {};   
\node[state]          (a8)  [right =of a7]   {};
\node[state]          (a9)  [right =of a8]   {}; 
\node[state]          (a5)  [above =of a9]   {};
\node[state]          (b0)  [right =of a6]   {}; 
\node[state]          (b1)  [right =of b0]   {};
\node[state]          (b2)  [right =of b1]   {}; 
\node[state]          (b3)  [right =of b2]   {};
\node[state]          (b4)  [right =of a9]   {};                                
\tikzset{every node/.style={fill=white}}
\tikzset{mystyle/.style={->,double=red}}  
\path (a4)     edge [mystyle]       node   {$0$} (a6)
      (a2)     edge [mystyle]       node   {$0$} (a7)
      (b0)     edge [mystyle]       node   {$0$} (b1);
\tikzset{mystyle/.style={->,double=blue}}  
\path (a3)     edge [mystyle]       node   {$1$} (a5)
      (a8)     edge [mystyle]       node   {$1$} (a9)
      (b2)     edge [mystyle]       node   {$1$} (b3);              
\tikzset{mystyle/.style={->,double=yellow}}  
\path (a0)     edge [mystyle]       node   {$\varepsilon$} (a1)
      (a1)     edge [mystyle]       node   {$\varepsilon$} (a2)
      (a1)     edge [mystyle]       node   {$\varepsilon$} (a3)
      (a1)     edge [mystyle]       node   {$\varepsilon$} (a4)
      (a6)     edge [mystyle]       node   {$\varepsilon$} (b0)
      (a7)     edge [mystyle]       node   {$\varepsilon$} (a8)
      (b1)     edge [mystyle]       node   {$\varepsilon$} (b2)
      (a9)     edge [mystyle]       node   {$\varepsilon$} (b4)
      (a5)     edge [mystyle]       node   {$\varepsilon$} (b4)
      (b3)     edge [mystyle]       node   {$\varepsilon$} (b4);
\end{tikzpicture}
\end{center}
\end{document}

Now, I want to add a yellow epsilon arrow from the node on the far left (a0) to the node on the far right (b4). However, I have absolutely no idea how to do this without the arrow cutting through the rest of the automata. Can I get some help here?

Answer 1

You can use [bend left] option as suggested in a comment, and give it an angle, such as [bend left=70], then the curve will leave then start and ending nodes at that angle, and thus the resulting path is symmetric.

(a0)   edge[mystyle, bend left=70] node {$\varepsilon$} (b4);

However, in this particular case, since the figure is assymetric, this way of producing the path looks a bit ugly (imho):

Through options in and out you can specify different angles for the endings of the path, and thus create an assymetric arc which fits better with the rest of the figure:

 (a0)   edge[mystyle, out=50,in=90] node {$\varepsilon$} (b4);