Given a binary tree, return the level order traversal of its nodes‘ values. (ie, from left to right, level by level).
For example:
Given binary tree [3,9,20,null,null,15,7],
3
/ 9 20
/ 15 7
return its level order traversal as:
[ [3], [9,20], [15,7] ]
1 # Definition for a binary tree node. 2 # class TreeNode: 3 # def __init__(self, x): 4 # self.val = x 5 # self.left = None 6 # self.right = None 7 8 class Solution: 9 def levelOrder(self, root: TreeNode) -> List[List[int]]: 10 res = [] 11 if root is None: 12 return res 13 from collections import deque 14 queue = deque() 15 queue.append(root) 16 while queue: 17 size = len(queue) 18 lst = [] 19 for i in range(size): 20 cur = queue.popleft() 21 lst.append(cur.val) 22 if cur.left: 23 queue.append(cur.left) 24 if cur.right: 25 queue.append(cur.right) 26 res.append(lst) 27 return res 28 29
[LC] 102. Binary Tree Level Order Traversal
原文：https://www.cnblogs.com/xuanlu/p/11711300.html