<h2> Problem Directory: /home/bvanderz/cs140/Labs/treeHeight </h2>
<h2> Problem Description </h2>
<p>
Write a recursive function to compute the height of a binary tree. The height of a binary tree can be recursively defined as follows:
<pre>
height(root) = max(height(left subtree), height(right subtree)) + 1
height(NULL) = -1
</pre>
The meaning of height(NULL) is -1 is that an empty tree has a height of -1. That means that a leaf, which has no children, will end up with a height of 0. 
<p>
  <hr>
  <h2> What To Do </h2>
<p>
  <ol>
    <li> You will modify the file named treeHeight.cpp. Put your function
      definition where the comment tells you to do so.
    <li> Compile your file into an executable named "treeHeight".
    <li> There are three input files named input1.txt, input2.txt, and input3.txt.
      You can test your program by using these files as input to your program.
    <li> There is an executable named "solution" that you can use to see
      the correct output. An example execution would be:
      <pre>
	./solution &lt; input1.txt
      </pre>
    <li> You can run the "gradeall" script to see if your program passes
      the test cases.
    <li> Get a TA to check you off when your function correctly passes the
      test cases.
   </ol>