使用Python向二叉树中缺少的节点添加值

class TreeNode:
    def __init__(self, value):
        self.value = value
        self.left = None
        self.right = None

def add_missing_node(root, value):
    if root is None:
        root = TreeNode(value)
    else:
        if root.left is None:
            root.left = TreeNode(value)
        elif root.right is None:
            root.right = TreeNode(value)
        else:
            # 如果左右子节点都已存在，则递归地向左子树添加节点
            add_missing_node(root.left, value)
    return root

# 创建一个二叉树
root = TreeNode(1)
root.left = TreeNode(2)
root.right = TreeNode(3)

# 向二叉树中添加缺少的节点值
root = add_missing_node(root, 4)
root = add_missing_node(root, 5)