leetcode -- Maximum Depth of Binary Tree -- 重点

https://leetcode.com/problems/maximum-depth-of-binary-tree/

recursive的方法最简单

class Solution(object):
    def maxDepth(self, root):
        """
        :type root: TreeNode
        :rtype: int
        """
        if not root:
            return 0
        return max(self.maxDepth(root.left), self.maxDepth(root.right)) + 1

要再查一下 iterative的方法怎么弄