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]
]
My code:
# Definition for a binary tree node.
# class TreeNode:
# def __init__(self, x):
# self.val = x
# self.left = None
# self.right = None
class Solution:
def levelOrder(self, root):
"""
:type root: TreeNode
:rtype: List[List[int]]
"""
#level = 1
if not root:
return []
final_res = [[root.val]]
to_traverse = [root.left, root.right]
while to_traverse:
res = []
Frontier = []
for node in to_traverse:
if node:
res.append(node.val)
Frontier.append(node.left)
Frontier.append(node.right)
to_traverse = Frontier
if res:
final_res.append(res)
return final_res
Solution: https://leetcode.com/problems/binary-tree-level-order-traversal/