n-ary-tree-level-order-traversal.py

# Given an n-ary tree, return the level order traversal of its nodes' values.
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# Nary-Tree input serialization is represented in their level order traversal, each group of children is separated by the null value (See examples).
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# Example 1:
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# Input: root = [1,null,3,2,4,null,5,6]
# Output: [[1],[3,2,4],[5,6]]
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# Example 2:
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# 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]]
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# Constraints:
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# 	The height of the n-ary tree is less than or equal to 1000
# 	The total number of nodes is between [0, 104]
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"""
# Definition for a Node.
class Node:
    def __init__(self, val=None, children=None):
        self.val = val
        self.children = children
"""

class Solution:
    def levelOrder(self, root: 'Node') -> List[List[int]]:
        if root is None:
            return []
        queue = [root]
        res = []
        while queue:
            nextLevel = []
            tmp = []
            for node in queue:
                tmp.append(node.val)
                for child in node.children:
                    nextLevel.append(child)
            res.append(tmp)
            queue = nextLevel
        return res