Golang : Convert lines of string into list for delete and insert operation



Tags : golang container-list push-delete-pop-remove linked-list text-string

Problem:

You want to convert a list of items in text format into a list. With the list, you want to search for a certain element by traversing the nodes. Once you found the element, you want to delete the element and insert a new element. i.e replace the element.

In another word, you have a text file that you want to transform into a list of nodes such as a double linked list where you can push, pop and traverse the tree with front and back functions. How to do that?

Solution:

Below is a program that will transform text string into a list with the help of container/list package. It also demonstrates how easy it is to remove a string that fit certain search value and insert a new element with the value of "Hello World". It also demonstrates how to convert the list back to a text string.

Here you go!


 package main

 import (
 "container/list"
 "fmt"
 "strings"
 )

 func main() {

 textString := `line 1
 line 2
 line 3
 line 4`

 lines := strings.Split(textString, "\n")

 // NOTE : To read from text file 
 // see https://www.socketloop.com/tutorials/golang-display-a-text-file-line-by-line-with-line-number-example

 listOfLines := list.New()

 // push each line into listOfLines
 for _, line := range lines {
 listOfLines.PushBack(line)
 }

 // before pop
 for e := listOfLines.Front(); e != nil; e = e.Next() {
 fmt.Println(e.Value.(string))
 }

 // search for line 3 and pop(remove) the element
 for e := listOfLines.Front(); e != nil; e = e.Next() {
 if e.Value.(string) == "line 3" {
 listOfLines.Remove(e)
 }
 }

 fmt.Println("=============================================")
 // after pop
 for e := listOfLines.Front(); e != nil; e = e.Next() {
 fmt.Println(e.Value.(string))
 }

 // now, let's insert Hello World after line 2
 for e := listOfLines.Front(); e != nil; e = e.Next() {
 if e.Value.(string) == "line 2" {
 listOfLines.InsertAfter("Hello World!", e)
 }
 }

 fmt.Println("=============================================")

 backToStringSlice := make([]string, listOfLines.Len())
 // after inserting Hello World and convert back to string
 // don't forget to add "\n" at the end of each line

 i := 0
 for e := listOfLines.Front(); e != nil; e = e.Next() {
 backToStringSlice[i] = e.Value.(string) + "\n"
 i++

 }

 // convert back from slice to string
 toString := fmt.Sprintf("%v", backToStringSlice)

 // remove the prefix [ and suffix ] leftover
 //fmt.Println(string(toString[0]))
 //fmt.Println(string(toString[len(toString)-1]))
 toString = toString[1 : len(toString)-1]

 // and we're back to text
 fmt.Println(toString)
 }

Output:

line 1

line 2

line 3

line 4

=============================================

line 1

line 2

line 4

=============================================

line 1

line 2

Hello World!

line 4

References:

Golang container/list package

turn text file into slice example

golang linked list example

golang container list insertbefore function example

  See also : Golang : Turn string or text file into slice example



Tags : golang container-list push-delete-pop-remove linked-list text-string

By Adam Ng

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