题目要求
Given an n-ary tree, return the level order traversal of its nodes' values. (ie, from left to right, level by level).
题目分析及思路
给定一棵N叉树，要求返回它的层次遍历结果。可以使用collections.deque来保存结点，按照每一层的长度来遍历结点。
python代码
"""
# Definition for a Node.
class Node:
def __init__(self, val, children):
self.val = val
self.children = children
"""
class Solution:
def levelOrder(self, root: 'Node') -> List[List[int]]:
order1 = []
q = collections.deque()
q.append(root)
while q:
order2 = []
size = len(q)
for _ in range(size):
node = q.popleft()
if not node:
continue
order2.append(node.val)
for child in node.children:
q.append(child)
if order2:
order1.append(order2)
return order1