102. Binary Tree Level Order Traversal

Question: Binary Tree Level Order Traversal
Solution

一個一個 level 慢慢掃 → BFS → queue

from collections import deque

class Solution:

def levelOrder(self, root: Optional[TreeNode]) -> List[List[int]]:

ans = list()

if root == None:

return ans

q = deque([root])

while q:

tmp = list()

for i in range(len(q)):

node = q.popleft()

tmp.append(node.val)

if node.left:

q.append(node.left)

if node.right:

q.append(node.right)

ans.append(tmp)

return ans

Video Solution