这一题需要熟悉树的层序遍历的方式,其实是用队列将每一层的子节点加进队列中,然后再依次遍历每一层的节点
class Solution: def PrintFromTopToBottom(self , root: TreeNode) -> List[int]: # write code here if not root: return [] queue = [root] res = [] while queue != []: nextNode = [] for node in queue: if node.left: nextNode.append(node.left) if node.right: nextNode.append(node.right) res.append(node.val) queue = nextNode return res