title: Is this a full binary tree?
body: <p>Here's the binary tree in question. The leaves are a, b, c, d and the edges are labelled 0 or 1.</p>
  
  <pre><code>    .
     / \
    a   .
       / \
      b   .
         / \
        c   d
  </code></pre>
  
  <p>It seems to me that it is a full binary tree, as every node is either a leaf or has two child nodes, however I have this feeling that we were told it is not a full binary tree. If not, why is it not?</p>
  
  <p>If a node has a child that is a leaf, does that not count as a child node?</p>