title: How to walk through a graph?
body: <p>I have the following tree</p>
  
  <pre><code>     1
      2 3
     4 5 6
    7 8 9 0
  </code></pre>
  
  <p>Now i want to walk through all possible paths trough the tree. It is always possible to move to adjacent numbers from the row below. For example </p>
  
  <p><code>1 2 4 7</code> or <code>1 2 5 8</code></p>
  
  <p>Any hints what is the best way to do that? I'm looking for a general hint, but in my implementation I have an ArrayList for each row.</p>