make a tree from a table using golang?

Question

I want to make a tree from a table. the table is as following:

OrgID   OrgName        parentID
A001    Dept           0 -----th top
A002    subDept1        A001
A003    sub_subDept    A002
A006    gran_subDept   A003
A004    subDept2        A001

and i want the result is as following,how to do it using go:

Dept

--subDept1

----sub_subDept

------gran_subDept

--subDept2

Be more specific what kind of table; mysql table? []Organization slice? mongoDB collection? And what type do you want the tree to be in? — ANisus, Apr 09 '14 at 09:18

score 10 · Accepted Answer · answered Apr 09 '14 at 10:31

If you want to parse the lines into a tree structure, this is a way to do it:

package main

import (
    "bufio"
    "fmt"
    "io"
    "os"
    "strings"
)

type Node struct {
    name     string
    children []*Node
}

var (
    nodeTable = map[string]*Node{}
    root      *Node
)

func add(id, name, parentId string) {
    fmt.Printf("add: id=%v name=%v parentId=%v\n", id, name, parentId)

    node := &Node{name: name, children: []*Node{}}

    if parentId == "0" {
        root = node
    } else {

        parent, ok := nodeTable[parentId]
        if !ok {
            fmt.Printf("add: parentId=%v: not found\n", parentId)
            return
        }

        parent.children = append(parent.children, node)
    }

    nodeTable[id] = node
}

func scan() {
    input := os.Stdin
    reader := bufio.NewReader(input)
    lineCount := 0
    for {
        lineCount++
        line, err := reader.ReadString('\n')
        if err == io.EOF {
            break
        }
        if err != nil {
            fmt.Printf("error reading lines: %v\n", err)
            return
        }
        tokens := strings.Fields(line)
        if t := len(tokens); t != 3 {
            fmt.Printf("bad input line %v: tokens=%d [%v]\n", lineCount, t, line)
            continue
        }
        add(tokens[0], tokens[1], tokens[2])
    }
}

func showNode(node *Node, prefix string) {
    if prefix == "" {
        fmt.Printf("%v\n\n", node.name)
    } else {
        fmt.Printf("%v %v\n\n", prefix, node.name)
    }
    for _, n := range node.children {
        showNode(n, prefix+"--")
    }
}

func show() {
    if root == nil {
        fmt.Printf("show: root node not found\n")
        return
    }
    fmt.Printf("RESULT:\n")
    showNode(root, "")
}

func main() {
    fmt.Printf("main: reading input from stdin\n")
    scan()
    fmt.Printf("main: reading input from stdin -- done\n")
    show()
    fmt.Printf("main: end\n")
}

score 5 · Answer 2 · answered Apr 09 '14 at 09:36

With the information provided in your question and comment, what could solve your problem is an ordinary recursive loop.

package main

import "fmt"

type Org struct {
    OrgID    string
    OrgName  string
    parentID string
}

func printTree(tbl []Org, parent string, depth int) {
    for _, r := range tbl {
        if r.parentID == parent {
            for i := 0; i < depth; i++ {
                fmt.Print("--")
            }
            fmt.Print(r.OrgName, "\n\n")
            printTree(tbl, r.OrgID, depth+1)
        }
    }
}

func main() {
    data := []Org{
        {"A001", "Dept", "0 -----th top"},
        {"A002", "subDept1", "A001"},
        {"A003", "sub_subDept", "A002"},
        {"A006", "gran_subDept", "A003"},
        {"A004", "subDept2", "A001"},
    }

    printTree(data, "0 -----th top", 0)
}

Result:

Dept

--subDept1

----sub_subDept

------gran_subDept

--subDept2

Playground: http://play.golang.org/p/27CQAhI8gf

Be aware that this recursive function might get stuck in an loop incase there if a parent is the descendant of its own child.

If you wish to have the result in json, you should add the desired json structure in your question. You can represent that output in many ways. — ANisus, Apr 09 '14 at 09:44

make a tree from a table using golang?

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