429-n-ary-tree-level-order-traversal

Given an n-ary tree, return the level order traversal of its nodes’ values.

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: [[1],[3,2,4],[5,6]] 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: [[1],[2,3,4,5],[6,7,8,9,10],[11,12,13],[14]]

My solution：

"""
# Definition for a Node.
class Node(object):
    def __init__(self, val=None, children=None):
        self.val = val
        self.children = children
"""
from collections import deque
class Solution(object):
    def levelOrder(self, root):
        """
        :type root: Node
        :rtype: List[List[int]]
        """
        queue = deque()
        queue.append(root)
        res = []
        if not root:
            return []
        while queue:
            item = []
            for i in range(len(queue)):
                cur = queue.popleft()
                item.append(cur.val)
                if cur.children:
                    queue.extend(cur.children)
            res.append(item)
        return res