title: how to find the height of a node in binary tree recursively
body: <pre><code>path = 0 # the lenght of the path
      while self.right != None or self.left != None:
          while self.right != None:
              self = self.right
              path = path +1 
          while self.left != None:
              self = self.left
              path = path +1
      return path
  </code></pre>
  
  <p>this is my sample code for find the Height, is defined as the length of the
  longest path by number of nodes from self to a leaf. The height of a leaf node is 1.</p>
  
  <p>it doesn't work. </p>