 depth first search.  The output records the distance to the other vertices, except where the vertices are not reachable
            starting from the first node A.
         </p><pre class="codeinput">d=dfs(A,1)
</pre><pre class="codeoutput">
d =

     0
     1
     3
     3
     2
     4
    -1
    -1
    -1

</pre><p>From this example, we see that vertices a-f are reachable from vertex a, but that verice g-i are not reachable.  Given the
            of the edges, this makes sense.
         </p>
         <