LC 0107 [M] Binary Tree Level Order Traversal II - ALawliet/algorithms GitHub Wiki
class Solution:
def levelOrderBottom(self, root: Optional[TreeNode]) -> List[List[int]]:
if not root: return []
Q = deque([root])
levels = deque()
while Q:
level = []
for _ in range(len(Q)):
node = Q.popleft()
level.append(node.val)
if node.left:
Q.append(node.left)
if node.right:
Q.append(node.right)
levels.appendleft(level)
return levels