二叉树问题---判断一棵树是否为完全二叉树

#判断一棵树是否为完全二叉树def isCBT(root):    if not root:        return True    isLeaf = False    queue = []    queue.append(root)    while queue:        root = queue.pop(0)        left = root.left        right = root.right        if (not left and right) or (isLeaf and (left  or right)):            return False        if left:            queue.append(left)        if right:            queue.append(right)        else:            isLeaf = True    return True