Imports System
Imports System.Text
Imports System.Collections.Generic
Module Module1
' Remove last n occurrences of a substring
Function RemoveLastNOccurrences(s As String, subStr As String, n As Integer) As String
Dim positions As New List(Of Integer)()
Dim pos As Integer = s.IndexOf(subStr)
' Find all occurrences
While pos <> -1
positions.Add(pos)
pos = s.IndexOf(subStr, pos + subStr.Length)
End While
Dim sb As New StringBuilder(s)
' Remove from the end
For i As Integer = positions.Count - 1 To 0 Step -1
If n = 0 Then Exit For
sb.Remove(positions(i), subStr.Length)
n -= 1
Next
Return sb.ToString()
End Function
' Remove extra spaces (collapse multiple spaces, trim ends)
Function RemoveExtraSpaces(s As String) As String
Dim parts = s.Trim().Split(New Char() {" "c}, StringSplitOptions.RemoveEmptyEntries)
Return String.Join(" ", parts)
End Function
Sub Main()
Dim text As String = "abc xyz xyz abc xyzabcxyz abc"
Dim result As String = RemoveLastNOccurrences(text, "xyz", 3)
Console.WriteLine(result)
Dim cleaned As String = RemoveExtraSpaces(result)
Console.WriteLine(cleaned)
End Sub
End Module
' run:
'
' abc xyz abc abc abc
' abc xyz abc abc abc
'
