问题
I would like to calculate all possible combinations in an array of digits (0 to 9), uppercase letters (A to Z) and lowercase letters (a to z).
Array contain only 10 digits or letters at time.
I'm trying this in vb.net but I found it a little confusing.
Anyone have an idea how to do this?
回答1:
Here's an iterative approach that would allow you to start the sequence from any position. This way you could stop the sequence, store the current value, then later restart it from the same position even if you closed the application (obviously you'd have to store that value somewhere like a text file).
This is simply a modified version of my code here: http://www.experts-exchange.com/Programming/Languages/.NET/Visual_Basic.NET/Q_23723548.html#a22452485
The Sleep() call is just so you can see the values going by in the Label:
Public Class Form1
Private Rev As Revision
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
' You can start from anywhere in the sequence by passing in a different starting value to the second parameter below:
Rev = New Revision("abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789", "aaaaaaaaaa")
Label1.Text = Rev.CurrentRevision
End Sub
Private Sub Form1_Shown(sender As Object, e As EventArgs) Handles Me.Shown
BackgroundWorker1.RunWorkerAsync()
End Sub
Private Sub BackgroundWorker1_DoWork(sender As Object, e As System.ComponentModel.DoWorkEventArgs) Handles BackgroundWorker1.DoWork
System.Threading.Thread.Sleep(100)
Dim curRevision As String = Rev.NextRevision
While curRevision.Length = 10
BackgroundWorker1.ReportProgress(-1, curRevision)
System.Threading.Thread.Sleep(50)
curRevision = Rev.NextRevision
End While
End Sub
Private Sub BackgroundWorker1_ProgressChanged(sender As Object, e As System.ComponentModel.ProgressChangedEventArgs) Handles BackgroundWorker1.ProgressChanged
Label1.Text = e.UserState
End Sub
End Class
Public Class Revision
Private chars As String
Private values() As Char
Private curRevision As System.Text.StringBuilder
Public Sub New()
Me.DefaultRevision()
End Sub
Public Sub New(ByVal validChars As String)
If validChars.Length > 0 Then
chars = validChars
values = chars.ToCharArray()
curRevision = New System.Text.StringBuilder(values(0))
Else
Me.DefaultRevision()
End If
End Sub
Public Sub New(ByVal validChars As String, ByVal startingRevision As String)
Me.New(validChars)
curRevision = New System.Text.StringBuilder(startingRevision)
Dim i As Integer
For i = 0 To curRevision.Length - 1
If Array.IndexOf(values, curRevision.Chars(i)) = -1 Then
curRevision = New System.Text.StringBuilder(values(0))
MessageBox.Show("Revision has been reset." & vbCrLf & "Current Revision = " & Me.CurrentRevision, "Starting Revision contains an Invalid Character", MessageBoxButtons.OK, MessageBoxIcon.Exclamation)
Exit For
End If
Next
End Sub
Private Sub DefaultRevision()
chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
values = chars.ToCharArray
curRevision = New System.Text.StringBuilder(values(0))
End Sub
Public ReadOnly Property ValidChars() As String
Get
Return chars
End Get
End Property
Public ReadOnly Property CurrentRevision() As String
Get
Return curRevision.ToString()
End Get
End Property
Public Function NextRevision(Optional ByVal numRevisions As Integer = 1) As String
Dim forward As Boolean = (numRevisions > 0)
numRevisions = Math.Abs(numRevisions)
Dim i As Integer
For i = 1 To numRevisions
If forward Then
Me.Increment()
Else
Me.Decrement()
End If
Next
Return Me.CurrentRevision
End Function
Private Sub Increment()
Dim curChar As Char = curRevision.Chars(curRevision.Length - 1)
Dim index As Integer = Array.IndexOf(values, curChar)
If index < (chars.Length - 1) Then
index = index + 1
curRevision.Chars(curRevision.Length - 1) = values(index)
Else
curRevision.Chars(curRevision.Length - 1) = values(0)
Dim i As Integer
Dim startPosition As Integer = curRevision.Length - 2
For i = startPosition To 0 Step -1
curChar = curRevision.Chars(i)
index = Array.IndexOf(values, curChar)
If index < (values.Length - 1) Then
index = index + 1
curRevision.Chars(i) = values(index)
Exit Sub
Else
curRevision.Chars(i) = values(0)
End If
Next
curRevision.Insert(0, values(0))
End If
End Sub
Private Sub Decrement()
Dim curChar As Char = curRevision.Chars(curRevision.Length - 1)
Dim index As Integer = Array.IndexOf(values, curChar)
If index > 0 Then
index = index - 1
curRevision.Chars(curRevision.Length - 1) = values(index)
Else
curRevision.Chars(curRevision.Length - 1) = values(values.Length - 1)
Dim i As Integer
Dim startPosition As Integer = curRevision.Length - 2
For i = startPosition To 0 Step -1
curChar = curRevision.Chars(i)
index = Array.IndexOf(values, curChar)
If index > 0 Then
index = index - 1
curRevision.Chars(i) = values(index)
Exit Sub
Else
curRevision.Chars(i) = values(values.Length - 1)
End If
Next
curRevision.Remove(0, 1)
If curRevision.Length = 0 Then
curRevision.Insert(0, values(0))
End If
End If
End Sub
End Class
回答2:
The number of combination of 10 places with 26*2+10=62 characters per each will give 62^10 different strings. If you want to store them in a memory.. well good luck. If you want to process them one by one..good luck as well. But generally the method is recursive (pseudocode:
perms(n, chars)
while (characters remaining in chars)
firstChar = getNextCharacterFrom(chars)
output <- firstChar + perms(n-1, chars)
来源：https://stackoverflow.com/questions/26981733/possible-combinations-calculator