def TreeDepth1(root):

	if None == root:

		return 0

	if None == root.left and None == root.right:

		return 1

	leftDepth = 0; rightDepth = 0

	if root.left:

		leftDepth = TreeDepth(root.left)

	if root.right:

		rightDepth = TreeDepth(root.right)

	return max(leftDepth, rightDepth) + 1

简洁点的

ef TreeDepth(root):

	if None == root:

		return 0

	return max(TreeDepth(root.left), TreeDepth(root.right)) + 1

代价将是不必要的递归