Imports System

Imports microsoft.visualbasic

​

Public Module Module1

    Public Sub Main()

        Dim arr(19) as node

        Dim inp as string

        Dim freeptr as integer = 0

        Dim currptr as integer 'not used'

        Dim frstptr as integer = 0

        Dim lastptr as integer = 0

        Dim inuse as integer

        for i = 0 to 19

        arr(i).value = ""

        arr(i).pointer = nullpointer

    next

    console.writeline("Enter 'del' to take a node out of the queue")

    console.writeline("Enter 'inp' to add a node to the queue")

    console.writeline("Enter 'prt' to view the current queue")

    console.writeline("Enter 'esc' to end the program")

    do

        inuse = 0

        for i = 0 to 19

        if arr(i).value <> ""

            inuse = inuse + 1

        end if

    next

        console.writeline("")

        console.writeline("Enter action")

        inp = console.readline()

        select case Lcase(inp)

        case Lcase("del")

        delete(arr, frstptr, inuse)

        case Lcase("inp")

        input(arr, freeptr, lastptr, inuse)

        case Lcase("prt")

        print(arr, frstptr, inuse)

        case Lcase("esc")

            'nothing happens

        case else

            console.writeline("Invalid entry")

        end select

    checkforfree(arr, freeptr)

    if frstptr = nullpointer

        frstptr = 0

    end if

    loop until Lcase(inp) = Lcase("esc")

    End Sub

public sub checkforfree(arr() as node, ByRef free as integer)

for i = 0 to 19

if arr(i).value = ""

    free = i

    i = 19

end if

next

end sub

​

public sub delete(arr() as node, ByRef first as integer, inuse as integer)

Dim temp as integer

if inuse <= 0

console.writeline("Sorry, the queue is empty :(")

else

console.writeline("{0} was taken out of the queue", arr(first).value)

temp = arr(first).pointer

arr(first).value = ""

arr(first).pointer = nullpointer

first = temp

end if

end sub

​

public sub input(arr() as node, free as integer, ByRef last as integer, inuse as integer)

Dim inp as string

if inuse >= 20

    console.writeline("Sorry, the queue is full :(")

else

    console.writeline("Enter value")

    inp = console.readline()

    arr(free).value = inp

    arr(free).pointer = nullpointer

    if inuse > 0

    arr(last).pointer = free

    end if

last = free

end if

end sub

​

public sub print(arr() as node, first as integer, inuse as integer)

dim pointtonext as integer = first

if inuse <= 0 

console.writeline("The queue is currently empty")

else

console.writeline("The queue currently contains the following:")

do

    console.writeline(arr(pointtonext).value)

    pointtonext = arr(pointtonext).pointer

loop until pointtonext = nullpointer

end if

end sub

​

    public structure node

    Dim value as string

    Dim pointer as integer

end structure

​

public const nullpointer as integer = -1

​

End Module