Homework Five
Tree Pretty Printing
Due: Thursday March 3

I am creating a program that uses a binary tree. For debugging purposes, I need a function that will print the contents of a tree in a format where the structure of the tree is evident. In other words, I not only need to see the values in the tree, but also what values are to the left and right of each other.

I created this test code to build a small tree that looks like this: 

       20
      /  \
     10  40
        /
       30
Your job is to write the print_tree function to create output such as: 
node 20 -- left child is 10, right child is 40 
node 10 -- left child is null, right child is null 
node 40 -- left child is 30, right child is null 
node 30 -- left child is null, right child is null