title: What is the definition for the height of a tree?
body: <p>I can't seem to find a definitive answer for this, I'm trying to do some elementary proofs on heaps but here's what's throwing me off a little bit:</p>
  
  <p><b>Is an empty tree valid?  If so, what is its height?</b><br>
  I would think this would be 0.</p>
  
  <p><b>What is the height of a tree with a single node?</b><br>
  I would think this would be 1 but I have seen definitions where it is 0 (and if this is the case then I don't know how to account for an empty tree).</p>