559\. Maximum Depth of N-ary Tree

Easy

Given a n-ary 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.

_Nary-Tree input serialization is represented in their level order traversal, each group of children is separated by the null value (See examples)._

**Example 1:**

![](https://assets.leetcode.com/uploads/2018/10/12/narytreeexample.png)

**Input:** root = [1,null,3,2,4,null,5,6]

**Output:** 3 

**Example 2:**

![](https://assets.leetcode.com/uploads/2019/11/08/sample_4_964.png)

**Input:** root = [1,null,2,3,4,5,null,null,6,7,null,8,null,9,10,null,null,11,null,12,null,13,null,null,14]

**Output:** 5 

**Constraints:**

*   The total number of nodes is in the range <code>[0, 10<sup>4</sup>]</code>.
*   The depth of the n-ary tree is less than or equal to `1000`.