A18737. 以下代码可以正确地按层换行输出二叉树的节点值。from collections import deque class TreeNode: def __init__(self, val=0, left=None, right=None): self.val = val self.left = left self.right = right def printByLevel(root): if no…

以下代码可以正确地按层换行输出二叉树的节点值。

from collections import deque
class TreeNode:
    def __init__(self, val=0, left=None, right=None):
        self.val = val
        self.left = left
        self.right = right
def printByLevel(root):
    if not root:
        return

    q = deque([root])

    while q:
        for i in range(len(q)):
            cur = q.popleft()
            print(cur.val, end=' ')

            if cur.left:
                q.append(cur.left)
            if cur.right:
                q.append(cur.right)
        print()