Imports System
Public Class Program
Public Shared Function longestCommonPrefix(ByVal sub1 As String, ByVal sub2 As String) As String
Dim min As Integer = Math.Min(sub1.Length, sub2.Length)
For i As Integer = 0 To min - 1
If sub1(i) <> sub2(i) Then
Return sub1.Substring(0, i)
End If
Next
Return sub1.Substring(0, min)
End Function
Public Shared Function longestRepeatingSubstring(ByVal s As String) As String
Dim lrs As String = ""
Dim size As Integer = s.Length
For i As Integer = 0 To size - 1
For j As Integer = i + 1 To size - 1
Dim lcp As String = longestCommonPrefix(s.Substring(i, size - i), s.Substring(j, size - j))
If lcp.Length > lrs.Length Then
lrs = lcp
End If
Next
Next
Return lrs
End Function
Public Shared Sub Main(ByVal args As String())
Dim s As String = "pythonphpjavacdartcppjavacsharp"
Console.WriteLine(longestRepeatingSubstring(s))
End Sub
End Class
' run:
'
' pjavac
'
