VB-2008 How to retrieve strings with largest numerical suffix in an array? - vb.net

Question

I got the following strings arrays
a.csv
a-1.csv
a-2.csv
a-3.csv
ab.csv
ab-1.csv
ab-2.csv
cccc.csv
cccc-1.csv
d.csv
In this strings arrays, it stores a series of test data, the naming conversion for each test data is as follows,
'unit name'+'-'+('suffix in single digit number')+'.csv'
The length of the unit name could be any length, but the suffix can only be single-digit number (1-9). For example for unit a, it undergoes 4 test in total, which are a.csv, a-1.csv, a-2.csv and a-3.csv. But because all of the first three test fails the specs, therefore only the last test data will be retrieved for analysis, which is a-3.csv.
So, for the final output, I only need those data which have the largest suffix for each unit, which gives me the output string array:
a-3.csv
ab-2.csv
cccc-1.csv
d.csv
How should I choose the correct files from the input string array according to the rules to get those test data only got the largest suffix.

Answer 1

Private Function Suffix(ByVal s As String) As String
s = IO.Path.GetFileNameWithoutExtension(s)
Dim pos = s.LastIndexOf("-"c)
Return If(pos = -1, s, s.Substring(0, pos))
End Function
Private Function Value(ByVal s As String) As Integer
s = IO.Path.GetFileNameWithoutExtension(s)
Dim pos = s.LastIndexOf("-"c)
Return If(pos = -1, 0, Integer.Parse(s.Substring(pos + 1)))
End Function
Dim arr() As String = New String() {"a.csv", "a-1.csv", "a-2.csv", "a-3.csv", "ab.csv", "ab-1.csv", "ab-2.csv", "cccc.csv", "cccc-1.csv", "d.csv"}
Dim largest = arr.GroupBy(Function(s) Suffix(s), StringComparer.OrdinalIgnoreCase) _
.Select(Function(g) g.OrderByDescending(Function(s) Value(s)).First())
For Each s In largest
Console.WriteLine(s)
Next

Answer 2

Though your question is not clear but I think you want to have the latest occurrence to be stored in a separate array. Here is how you can achieve that:
Dim arrayInput As List(Of String) = New List(Of String)
arrayInput.Add("a.csv")
arrayInput.Add("a-1.csv")
arrayInput.Add("a-2.csv")
arrayInput.Add("a-3.csv")
arrayInput.Add("b.csv")
arrayInput.Add("b-1.csv")
arrayInput.Add("b-2.csv")
arrayInput.Add("c.csv")
arrayInput.Add("c-1.csv")
arrayInput.Add("d.csv")
Dim arrayOutput As List(Of String) = New List(Of String)
Dim strTemp As String = arrayInput(0)
Dim startingChar As String = strTemp.Substring(0, 1)
For Each item As String In arrayInput
If Not startingChar.Equals(item.Substring(0, 1), StringComparison.OrdinalIgnoreCase) Then
arrayOutput.Add(strTemp)
startingChar = item.Substring(0, 1)
End If
strTemp = item
Next
arrayOutput.Add(strTemp)
You have the required result in arrayOutput. Let me know if you wanted something else instead.