Imports System
Imports System.Collections.Generic
Imports System.Text.RegularExpressions
Module Module1
Function GroupByFirstNLetters(s As String, Optional n As Integer = 3) _
As Dictionary(Of String, List(Of String))
Dim groups As New Dictionary(Of String, List(Of String))()
Dim regex As New Regex("[A-Za-z]+")
Dim matches = regex.Matches(s.ToLower())
For Each m As Match In matches
Dim word = m.Value
If word.Length >= n Then
Dim prefix = word.Substring(0, n)
If Not groups.ContainsKey(prefix) Then
groups(prefix) = New List(Of String)()
End If
groups(prefix).Add(word)
End If
Next
Return groups
End Function
Sub Main()
Dim s As String =
"The lowly inhabitants of the lowland were surprised to see " &
"the lower branches of the trees."
Dim groups = GroupByFirstNLetters(s, 3)
' First print style
For Each kv In groups
Console.WriteLine($"{kv.Key} : [{String.Join(", ", kv.Value)}]")
Next
Console.WriteLine()
' Second print style
For Each kv In groups
Console.WriteLine($"{kv.Key}: {String.Join(", ", kv.Value)}")
Next
End Sub
End Module
' run:
'
' the : [the, the, the, the]
' low : [lowly, lowland, lower]
' inh : [inhabitants]
' wer : [were]
' sur : [surprised]
' see : [see]
' bra : [branches]
' tre : [trees]
'
' the: the, the, the, the
' low: lowly, lowland, lower
' inh: inhabitants
' wer: were
' sur: surprised
' see: see
' bra: branches
' tre: trees
'
