title: Is there any simple example to explain ullmann algorithm
body: <p>Im a freshman in learning the graph theory. Im learning the (sub)graph isomorphism now. there are two important algorithms: <em>Ullmann's algorithm</em> and <em>vf2</em>. </p>
  
  <p>I have read the paper of Ullmann`s: <em>An algorithm for Subgraph Isomorphism</em>. I also googled it and google gave me a lot of applications of it, but I cannot understand the procedures of the algorithm. </p>
  
  <p>Could you give me a simple explanation?</p>