Imports System
Imports System.Collections.Generic
Module Module1
Function GetMissingAlphabetChars(input As String) As List(Of Char)
Dim present(25) As Boolean
' Normalize input: lowercase + keep only a..z
For Each ch As Char In input.ToLower()
If ch >= "a"c AndAlso ch <= "z"c Then
present(Convert.ToInt32(ch) - Convert.ToInt32("a"c)) = True
End If
Next
' Collect missing letters
Dim missing As New List(Of Char)
For i As Integer = 0 To 25
If Not present(i) Then
missing.Add(Convert.ToChar(Convert.ToInt32("a"c) + i))
End If
Next
Return missing
End Function
Sub Main()
Dim missing = GetMissingAlphabetChars("VB.NET Programming")
For Each ch As Char In missing
Console.WriteLine(ch)
Next
End Sub
End Module
' run:
'
' c
' d
' f
' h
' j
' k
' l
' q
' s
' u
' w
' x
' y
' z
'
