\begin{frame}{Nondeterministic Finite Automata}
  \begin{goal}{}
    NFAs are defined like DFAs, except that NFAs allow for:
    \begin{itemize}
      \item \emph{Multiple starting states}.
      \item \emph{Any number of outgoing arrows} with the same label.
      \item \emph{Empty steps}: arrows labelled $\lambda$ (do not consume input).
    \end{itemize}
  \end{goal}

  \begin{exampleblock}{}
    \begin{center}
      \vspace{-.5ex}
      \input{tikz/nfa1.tex}
      \vspace{-1ex}
    \end{center}
    Note that:
    \begin{itemize}
      \item both $q_0$ and $q_2$ are starting states
      \item the state $q_1$ has two outgoing arrows with label $b$
      \item there is an empty step from $q_0$ to $q_1$ 
    \end{itemize}
  \end{exampleblock}    
\end{frame}