title: “104 Maximum Depth of Binary Tree” permalink: /leetcode/tree/104 layout: single classes: wide tags: [leetcode, tree, easy] date: 2018-07-22 sidebar: nav: “leetcode” —

Original Description: Given a binary tree, find its maximum depth. The maximum depth is the number of nodes along the longest path from the root node down to the farthest leaf node. Note: A leaf is a node with no children.

• 要求： 给一个binary tree。

• 返回： 求其深度

• 例子：
  • input: Given binary tree [3,9,20,null,null,15,7]
  • output: 3

Solution

递归得求出左右子树的深度，选择其中较大的。

# Definition for a binary tree node.
# class TreeNode(object):
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None
class Solution(object):
    def maxDepth(self, root):
        """
        :type root: TreeNode
        :rtype: int
        """
        # https://www.cnblogs.com/zuoyuan/p/3782275.html
        if root == None:
            return 0
        else:
            return max(self.maxDepth(root.left), self.maxDepth(root.right)) + 1