How to draw two Tikz pictures that are parallel to each other?

Question

I want to draw two automaton figures next to each other; however I can't put them in one \begin{} \end{} tag because the node distance can be changed, further the distance between two pictures is also different. A minimal example would be greatly appreciated. Thank you.

\begin{tikzpicture}[shorten >=1pt,node distance=2cm,on grid,auto] 
    \node[state,initial]    (q_0)                   {$q_0$}; 
    \node[state,accepting]  (q_1)   [right=of q_0]  {$q_1$}; 
    \node[state]            (q_2)   [right=of q_1]  {$q_2$}; 

    \path[->]
    (q_0) edge                  node {a}            (q_1)
    (q_1) edge                  node {$\lambda$}    (q_2)
    (q_2) edge  [bend right]    node {$\lambda$}    (q_0)
    ; %end path 
\end{tikzpicture}

Answer 1

If the two pictures can stay on one line, it's nothing more than

\begin{tikzpicture}
<code for the first picture>
\end{tikzpicture}
\begin{tikzpicture}
<code for the second picture>
\end{tikzpicture}

They will be aligned at their bottom.

Answer 2

You could use a minipage:

\noindent
\begin{minipage}{.5\textwidth}
\centering
\begin{tikzpicture}
     <code for the first picture>
\end{tikzpicture}
\end{minipage}%
\begin{minipage}{.5\textwidth}
\centering
\begin{tikzpicture}
<code for the second picture>
\end{tikzpicture}
\end{minipage}

Or else a subfloat (using the subfig package):

\begin{figure}
\subfloat[first caption here]
{
\begin{tikzpicture}
     <code for the first picture>
\end{tikzpicture}
}
\subfloat[second caption here]
{
\begin{tikzpicture}
     <code for the second picture>
\end{tikzpicture}
}
\end{figure}

Answer 3

This is my solution based on the following example from TikZ tutorial http://www.texample.net/tikz/examples/nodetutorial/

\begin{tikzpicture}[shorten >=1pt,node distance=2cm,on grid,auto]
    \begin{scope}
        \node[state,initial]    (q_1)                           {$q_1$}; 
        \node[state,accepting]  (q_2)   [right=of q_1]          {$q_2$}; 
        \node[state]            (q_3)   [below right=of q_1]    {$q_3$}; 

        \path[->]
        (q_1) edge  [bend left]     node {a}            (q_2)
        (q_1) edge  [loop above]    node {b}            (q_1)
        (q_2) edge  [bend left]     node {a,b}          (q_3)
        (q_3) edge  [bend left]     node {a}            (q_2)
        (q_3) edge  [bend left]     node {b}            (q_1)
        ;
    \end{scope}

    \begin{scope}[xshift=10cm]
        \node[state,initial]    (q_1)                           {$q_1$}; 
        \node[state,accepting]  (q_2)   [right=of q_1]          {$q_2$}; 
        \node[state]            (q_3)   [below right=of q_1]    {$q_3$}; 

        \path[->]
        (q_1) edge  [bend left]     node {a}            (q_2)
        (q_1) edge  [loop above]    node {b}            (q_1)
        (q_2) edge  [bend left]     node {a,b}          (q_3)
        (q_3) edge  [bend left]     node {a}            (q_2)
        (q_3) edge  [bend left]     node {b}            (q_1)
        ;
    \end{scope}
\end{tikzpicture}