A28575. 以下关于完全二叉树的代码描述，正确的是（ ）。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 is_complete_tree(root): i…

以下关于完全二叉树的代码描述，正确的是（    ）。

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 is_complete_tree(root):
	if root is None:
		return True

	q = deque()
	q.append(root)
	has_null = False

	while q:
		node = q.popleft()
		if node is None:
			has_null = True
		else:
			if has_null:
				return False
			q.append(node.left)
			q.append(node.right)

	return True