需求

我们有如下的树型结构

想统一给这样的数据，添加目录索引，变成这样

我们知道从人眼看，只需要从上到下扫描就行了，可这要放在程序中可怎么写，很多时候你觉得简单的东西不一定简单，这就像你觉得"不存在最大的正整数"很正常，但是让你证明你却不会。

talk is cheap！两种实现方法奉上~

方法一：逐层遍历添加大纲

比如第一层添加x，第二层添加x.x，第三层添加x.x.x，如下图

这种实现需要借助一个队列，python代码如下

def add_tree_index_iterative(tree_list):
    for i, v in enumerate(tree_list):
        v['index'] = i + 1
        q.append(v)

    while q:
        v = q.pop(0)  # 出队列
        if v['children']:
            for i, node in enumerate(v['children']):
                node['index'] = f'{v["index"]}.{i + 1}'
                q.append(node)  # 入队列

python中的list的append和pop(0)分别对应了队列的入队和出队操作

方法二：深度遍历添加大纲

就是每次都走到头添加完了再回来

这种一次走到头的遍历需要用递归实现，层层深入

def add_tree_index_recursive(tree_list, parent_index=""):
    for i, v in enumerate(tree_list):
        if not parent_index:
            v['index'] = i + 1
        else:
            v['index'] = f'{parent_index}.{i + 1}'
        if v['children']:
            add_tree_index_recursive(v['children'], v['index'])

测试结果

原始数据如下

[
    {
        "id": 1,
        "parent_id": 0,
        "name": "A",
        "children": [
            {
                "id": 2,
                "parent_id": 1,
                "name": "AA",
                "children": []
            },
            {
                "id": 3,
                "parent_id": 1,
                "name": "AB",
                "children": [
                    {
                        "id": 4,
                        "parent_id": 3,
                        "name": "ABA",
                        "children": []
                    },
                    {
                        "id": 5,
                        "parent_id": 3,
                        "name": "ABB",
                        "children": []
                    },
                    {
                        "id": 6,
                        "parent_id": 3,
                        "name": "ABC",
                        "children": []
                    }
                ]
            },
            {
                "id": 7,
                "parent_id": 1,
                "name": "AC",
                "children": [
                    {
                        "id": 8,
                        "parent_id": 7,
                        "name": "ACA",
                        "children": [
                            {
                                "id": 9,
                                "parent_id": 8,
                                "name": "ACAA",
                                "children": []
                            },
                            {
                                "id": 10,
                                "parent_id": 8,
                                "name": "ACAB",
                                "children": []
                            }
                        ]
                    }
                ]
            }
        ]
    }
]

经过添加大纲函数add_tree_index_recursive或add_tree_index_iterative处理后，会给每个节点添加对应的Index字段，如下