[leetcode] 429. N-ary Tree Level Order Traversal

Description

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]]

Constraints:

• The height of the n-ary tree is less than or equal to 1000
• The total number of nodes is between [0, 10^4]

分析

题目的意思是：实现一个n叉树的层序遍历。跟二叉树差不多，用层序遍历就行了。

代码

"""
# 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 []
        q=collections.deque()
        q.append(root)
        res=[]
        while(q):
            n=len(q)
            ans=[]
            for i in range(n):
                node=q.popleft()
                ans.append(node.val)
                for child in node.children:
                    q.append(child)
            res.append(ans)
        return res