Problem statement

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

Solution

Just traverse tree with for example dfs.

Complexity

Time complexity is O(n), space complexity is $(h+N), where h is height of tree and N is maximum number of children of any node.

Code

class Solution:
    def maxDepth(self, root):
        if not root: return 0
        depth = 0
        for child in root.children:
            depth = max(depth, self.maxDepth(child))
        return depth + 1