Public Class Form1
    Structure LinkedList
        Dim Pointer As Integer
        Dim Data As String
    End Structure
    Dim NextFree As Integer = 5
    Dim StartPointer As Integer = 3
    Dim node(10) As LinkedList

    Private Sub Form1_Load(sender As System.Object, e As System.EventArgs) Handles MyBase.Load
        node(1).Data = "Cake"
        node(2).Data = "Biscuit"
        node(3).Data = "Apple"
        node(4).Data = "Bun"
        node(1).Pointer = 0
        node(2).Pointer = 4
        node(3).Pointer = 2
        node(4).Pointer = 1
        Call UpdateList()
    End Sub
    Sub UpdateList()

        If NextFree = 11 Then
            MsgBox("No space left")
        Else
            lstOutput.Items.Clear()
            For i = 1 To NextFree
                If Not String.IsNullOrEmpty(node(i).Data) Then
                    lstOutput.Items.Add(node(i).Data)
                End If
            Next i
        End If
    End Sub
    Private Sub btnExit_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnExit.Click
        Me.Close()
        End
    End Sub

    Private Sub btnAdd_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnAdd.Click
        Dim item As String = InputBox("Please Insert data to add")
        node(NextFree).Data = item
        If item < node(StartPointer).Data Then
            Dim temp As String = NextFree
            NextFree = node(NextFree).Pointer
            node(temp).Pointer = StartPointer
            StartPointer = temp
        End If
        NextFree += 1
        Call UpdateList()
    End Sub

    Private Sub btnRemove_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnRemove.Click
        Dim item As String = lstOutput.SelectedItem
        Dim itemPointer, itemAddr As Integer
        For i = 1 To NextFree
            If item = node(i).Data Then
                itemPointer = node(i).Pointer
                itemAddr = i
            End If
            Next i
        Dim temp As String = NextFree
        NextFree = itemAddr
        node(itemAddr - 1).Pointer = node(itemAddr).Pointer
        node(itemAddr).Pointer = temp
        NextFree -= 1
        node(itemAddr).Data = Nothing
        node(itemAddr).Pointer = Nothing
        Call UpdateList()
    End Sub

    Private Sub btnSearch_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnSearch.Click
        Dim item As String = InputBox("Please specify your search query")
        Dim result As Integer
        Dim status As Boolean
        For i = 1 To NextFree
            If item = node(i).Data Then
                MsgBox("Item has been found with following addr " & node(i).Pointer)
                result = node(i).Pointer
                status = True
            End If
        Next
        If status = False And result = Nothing Then
            MsgBox("No data has been found please try again")
        End If

    End Sub
End Class