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102.py
48 lines (43 loc) · 1.12 KB
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102.py
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# 102. Binary Tree Level Order Traversal
# 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]
# ]
# Definition for a binary tree node.
# class TreeNode:
# def __init__(self, x):
# self.val = x
# self.left = None
# self.right = None
from typing import List
from queue import Queue
class Solution:
def levelOrder(self, root: TreeNode) -> List[List[int]]:
results = []
if not root:
return results
q1 = Queue()
q2 = Queue()
q1.put(root)
while q1.qsize() > 0:
tmp = []
while q1.qsize() > 0:
node = q1.get()
tmp.append(node.val)
if node.left:
q2.put(node.left)
if node.right:
q2.put(node.right)
results.append(tmp)
q1, q2 = q2, q1
return results