擅长:python、mysql、java
<p>这应该做到:</p>
<pre><code>def countNodes(tree):
if tree is None:
return 0
left = tree.get_left_subtree()
rght = tree.get_right_subtree()
return (0 if left is None or rght is None else 1) \
+ countNodes(left) + countNodes(rght)
</code></pre>