go语言实现递归，扁平转为树形，同时添加层级标识

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原始数据结构

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[
  {
    "id": "1",
    "pid": "0"
  },
  {
    "id": "2",
    "pid": "1"
  },
  {
    "id": "3",
    "pid": "1"
  },
  {
    "id": "4",
    "pid": "0"
  },
  {
    "id": "5",
    "pid": "4"
  },
  {
    "id": "6",
    "pid": "4"
  },
  {
    "id": "7",
    "pid": "3"
  },
  {
    "id": "8",
    "pid": "3"
  }
]

目标数据结构

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[
  {
    "id": "1",
    "pid": "0",
    "level": 0,
    "children": [
      {
        "id": "2",
        "pid": "1",
        "level": 1
      },
      {
        "id": "3",
        "pid": "1",
        "level": 1,
        "children": [
          {
            "id": "7",
            "pid": "3",
            "level": 2
          },
          {
            "id": "8",
            "pid": "3",
            "level": 2
          }
        ]
      }
    ]
  },
  {
    "id": "4",
    "pid": "0",
    "level": 0,
    "children": [
      {
        "id": "5",
        "pid": "4",
        "level": 1
      },
      {
        "id": "6",
        "pid": "4",
        "level": 1
      }
    ]
  }
]

go 实现的核心函数

指定pid根节点和level根层标识

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func handle(pid string, level int8) []d {
    var tree []d
    for _, v := range data {
        if v.Pid == pid {
            var children []d
            children = append(children, handle(v.ID, level+1)...)
            tree = append(tree, d{
                Level:    level,
                ID:       v.ID,
                Pid:      v.Pid,
                Children: children,
            })
        }
    }
    return tree
}

完整代码，粘贴即可运行

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package main

import (
    "bytes"
    "encoding/json"
    "log"
    "os"
)

type dataSource struct {
    ID  string `json:"id"`
    Pid string `json:"pid"`
}

type d struct {
    Level    int8   `json:"level"`
    ID       string `json:"id"`
    Pid      string `json:"pid"`
    Children []d    `json:"children"`
}

var data = []*dataSource{
    {
        ID:  "1",
        Pid: "0",
    },
    {
        ID:  "2",
        Pid: "1",
    },
    {
        ID:  "3",
        Pid: "1",
    }, {
        ID:  "4",
        Pid: "0",
    }, {
        ID:  "5",
        Pid: "4",
    },
    {
        ID:  "6",
        Pid: "4",
    },
    {
        ID:  "7",
        Pid: "3",
    },
    {
        ID:  "8",
        Pid: "3",
    },
}

func handle(pid string, level int8) []d {
    var tree []d
    for _, v := range data {
        if v.Pid == pid {
            var children []d
            children = append(children, handle(v.ID, level+1)...)
            tree = append(tree, d{
                Level:    level,
                ID:       v.ID,
                Pid:      v.Pid,
                Children: children,
            })
        }
    }
    return tree
}

func main() {
    root := handle("0", 0)
    b, _ := json.Marshal(root)

    var out bytes.Buffer
    err := json.Indent(&out, b, "", "\t")

    if err != nil {
        log.Fatalln(err)
    }

    out.WriteTo(os.Stdout)
}

输出结果

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[
  {
    "level": 0,
    "id": "1",
    "pid": "0",
    "children": [
      {
        "level": 1,
        "id": "2",
        "pid": "1",
        "children": null
      },
      {
        "level": 1,
        "id": "3",
        "pid": "1",
        "children": [
          {
            "level": 2,
            "id": "7",
            "pid": "3",
            "children": null
          },
          {
            "level": 2,
            "id": "8",
            "pid": "3",
            "children": null
          }
        ]
      }
    ]
  },
  {
    "level": 0,
    "id": "4",
    "pid": "0",
    "children": [
      {
        "level": 1,
        "id": "5",
        "pid": "4",
        "children": null
      },
      {
        "level": 1,
        "id": "6",
        "pid": "4",
        "children": null
      }
    ]
  }
]
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