leetcode: 104. Maximum Depth of Binary Tree

Difficulty

Easy.

Problem

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.

Example:

Given binary tree [3,9,20,null,null,15,7],

    3
   / \
  9  20
    /  \
   15   7
return its depth = 3.

AC

# Definition for a binary tree node.
# class TreeNode(object):
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None


class Solution():
    def maxDepth(self, root):
        if not root:
            return 0
        else:
            return max(self.maxDepth(root.left), self.maxDepth(root.right))+1