LeetCode 559. Maximum Depth of N-ary Tree



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:

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

Example 2:

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


  • The depth of the n-ary tree is less than or equal to 1000.
  • The total number of nodes is between [0, 104].


Traverse the tree and all the children nodes and record the maximum depth.

Python Solution

# Definition for a Node.
class Node:
    def __init__(self, val=None, children=None):
        self.val = val
        self.children = children

class Solution:
    def maxDepth(self, root: 'Node') -> int:        
        self.max_depth = 0
        self.traverse(root, 1)
        return self.max_depth
    def traverse(self, root, depth):
        if not root:
        self.max_depth = max(self.max_depth, depth)
        for child in root.children:
            self.traverse(child, depth + 1)
  • Time Complexity: O(N).
  • Space Complexity: O(N).

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