Imports System
Public Class Program
Public Shared Function GetLongestSubstring(ByVal str As String) As String
Dim start As Integer = 0, end_ As Integer = 0, max As Integer = 0
Dim size As Integer = str.Length
For i As Integer = 0 To size - 1 - 1
For j As Integer = i + 1 To size - 1
If str(i) = str(j) Then
Dim temp As Integer = Math.Abs(j - i - 1)
If temp > max Then
max = temp
start = i + 1
end_ = j
End If
End If
Next
Next
Return str.Substring(start, end_ - start)
End Function
Public Shared Sub Main(ByVal args As String())
Dim str As String = "zXoDvbnetprogrammingDkmq"
Dim result As String = GetLongestSubstring(str)
Console.Write(result)
End Sub
End Class
' run:
'
' vbnetprogramming
'
