What should i add to random number generator coding, so numbers wont repeat themselves more times in a row?
My random number generator looks like this:
Dim rn As New Random
TextBox1.Text = rn.Next(1, 4)
If TextBox1.Text = 1 Then
Form4.Show()
Form4.Timer1.Start()
End If
If TextBox1.Text = 2 Then
Form7.Show()
Form7.Timer1.Start()
End If
If TextBox1.Text = 3 Then
Form8.Show()
Form8.Timer1.Start()
End If
Given N (at present N = 3 but it could be something else, as you say), try to construct a random permutation of 1, ..., N, then open the text boxes in the order that is generated. Note that that means you're generating N numbers at a time and using them all up, then generating N more. Search for "random permutation" to find an algorithm.
Move your Random instance, "rn", out to Class (Form) level so it only gets created ONCE for the Form, and the same instance gets used over and over:
Public Class Form1
Private rn As New Random
Private Sub SomeMethod()
TextBox1.Text = rn.Next(1, 4)
If TextBox1.Text = 1 Then
Form4.Show()
Form4.Timer1.Start()
End If
If TextBox1.Text = 2 Then
Form7.Show()
Form7.Timer1.Start()
End If
If TextBox1.Text = 3 Then
Form8.Show()
Form8.Timer1.Start()
End If
End Sub
End Class
To get a random integer value between 1 and N (inclusive) you can use the following.
CInt(Math.Ceiling(Rnd() * n))
If you want each number only used once, you need to do something like this:
Const FirstNumber As Integer = 1
Const LastNumber As Integer = 5
' Fill the list with numbers
Dim numberList as New List(Of Integer)
For i As Integer = FirstNumber To LastNumber Step 1
numberList.Add(i)
Next i
Dim rand as New Random()
While numberList.Count > 0
' draw a random number from the list
Dim randomIndex As Integer = rand.Next(0, numberList.Count - 1)
Dim randomNumber As Integer = numberList(randomIndex)
' Do stuff with the number here
TextBox1.Text = randomNumber
' remove the number from the list so it can't be used again
numberList.RemoveAt(randomIndex)
End While
Related
enter image description hereWrite a program to display 1000 8-character random user IDs in a text box after you click a button. Make sure the program verifies that none of the IDs are identical. Each userid should include a mixture of alphabetic characters and numbers.
What I have so far, which could be enough to get by as a random ID generator alone, but it does not loop 1000 times to be displayed in the label, and doesn't check for repeated ID's.
Public Class Form1
Private Sub btnGenerateRandomID_Click(sender As Object, e As EventArgs) Handles btnGenerateRandomID.Click
Dim rand As New Random
Dim char1 As String
Dim char2 As String
Dim char3 As String
Dim char4 As String
Dim char5 As String
Dim char6 As String
Dim char7 As String
Dim char8 As String
char1 = ChrW(rand.Next(Asc("A"), Asc("Z") + 1))
char2 = ChrW(rand.Next(Asc("A"), Asc("Z") + 1))
char3 = ChrW(rand.Next(Asc("A"), Asc("Z") + 1))
char4 = ChrW(rand.Next(Asc("A"), Asc("Z") + 1))
char5 = rand.Next(0, 9)
char6 = rand.Next(0, 9)
char7 = rand.Next(0, 9)
char8 = rand.Next(0, 9)
lblRandomId.Text = char1 + char2 + char3 + char4 + char5 + char6 + char7 + char8
End Sub
End Class
Thanks.
EDIT:
Public Class Form1
'Write a program to display 1000 8-character random user IDs in a text
'box after you click a button. Make sure the program verifies that none Of the IDs are identical.
'Each userid should include a mixture Of alphabetic characters And numbers.
Private Sub btnGenerateRandomID_Click(sender As Object, e As EventArgs) Handles btnGenerateRandomID.Click
Dim strChar As String = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789"
Dim rand As New Random
Dim strID As String = ""
For count_ids As Integer = 0 To 999
For count_chars As Integer = 0 To 7
strID += strChar(rand.Next(0, 62))
Next count_chars
lblRandomId.Text = strID
Next
End Sub
End Class
Here is the actual question "Q. Write a program to display 1000 8-character random user IDs in a text box after you click a button. Make sure the program verifies that none of the IDs are identical. Each userid should include a mixture of alphabetic characters and numbers.
Explain your program in your essay, with screenshots. Include a paragraph on the random number generator used in Visual Basic, and answer the question: how should the random number generator be best seeded?"
First of all, Welcome to StackOverflow,
From what i understand from your post you want to generate 1000 8 Character long Unique ID's
First of all we declare our variables
Dim Characters As String = "AZERTYUIOPQSDFGHJKLMWXCVBN0123456789" 'Declare All Characters on one string
Dim IDsList As New List(Of String) With {.Capacity = 1000} 'You can limit the capacity to 1000
Dim Id As String = ""
Dim Rand As New Random
Now we begin to genearte ID's and add them to IDsList using a nested loop
For i As Integer = 0 To 999 'This is a Zero Based Index so 999 is actually 1000
For _i As Integer = 0 To 7 'This also means 7 is 8
Id += Characters(Rand.Next(0, 36))
Next
IDsList.Add(Id)
Id = ""
Next
'You can Check for duplicates by adding this piece of code or use the next one instead
Dim NoDupesIDsList As New List(Of String)
NoDupesIDsList = IDsList.Distinct.ToList
For i As Integer = 0 To 999 'This is a Zero Based Index so 999 is actually 1000
For _i As Integer = 0 To 7 'This also means 7 is 8
Id += Characters(Rand.Next(0, 36))
Next
If not IDsList.contains(Id) then
IDsList.Add(Id)
End if
Id = ""
Next
Use a Textbox with multiline and scroll bar for better experience
Feel free to ask me anything via comments
PS: I tested my method and it's working , enjoy it !
This function will return the ASCII characters between 48 an 122. That will include some characters that are not letters or numbers but this makes the ids even more unique and simplifies the code.
The For loop builds the ids with a length of 8. Then the id is checked for uniqueness with the .Contains method. Only if it is not in the list, it is added to the list and the counter is incremented.
Private Rnd As New Random
Private Function GetListOfIDs() As List(Of String)
Dim Counter As Integer
Dim lst As New List(Of String)
Dim id As String = ""
Do While Counter < 1000
id = ""
For i = 0 To 7
id &= Chr(Rnd.Next(48, 123))
Next
If Not lst.Contains(id) Then
lst.Add(id)
Counter += 1
End If
Loop
Return lst
End Function
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
Dim lst = GetListOfIDs()
TextBox1.Text = String.Join(vbCrLf, lst)
End Sub
EDIT
As per suggestion by Caius Jard in comments I have added a solution using a HashSet. Same idea only a HashSet will not accept duplicate entries. The .Add method returns a boolean telling you if the Add was successful.
Private Function GetListOfIDs() As HashSet(Of String)
Dim hs As New HashSet(Of String)
Dim id As String = ""
Do While hs.Count < 1001
id = ""
For i = 0 To 7
id &= Chr(Rnd.Next(48, 123))
Next
If hs.Add(id) Then
Counter += 1
End If
Loop
Return hs
End Function
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
Dim hs = BuildHashSet()
TextBox1.Text = String.Join(vbCrLf, hs)
End Sub
This method is probably more efficient because a HashSet is designed for hight performance. For 1000 items I did not notice any difference in the user interface. The text box updated immediately with both methods.
This will create the names:
Function RandomName(length As Integer) As String
Shared rnd As New Random()
Shared corpus() As Char = "ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789".ToCharArray()
Return New String(Enumerable.Range(0, length).Select(Function(c) corpus(rnd.Next(corpus.Length))).ToArray())
End Function
Iterator Function GetUniqueNames(length As Integer, count As Integer) As IEnumerable(Of String)
Dim names As New HashSet(Of String)
For i As Integer = 0 To count
Dim name As String = RandomName(length)
While names.Contains(name)
'Potential (but unlikely) halting problem
name = RandomName(length)
End While
names.Add(name)
Yield name
Next
End Function
Dim uniqueNames = GetUniqueNames(8, 1000)
But do you really want to display 1000 of them in a single label?
lblRandomId.Text = string.Join(vbCrLf, uniqueNames)
Let's talk about your code.
Dim strChar As String = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789"
This assignment will work in your loop because a String is really an array of Char. This is why you can refer to an index in the string.
Dim rand As New Random()
The .net Random class provides a seed for Random based on system time. Only rarely would you want to provide a seed.
From the docs https://learn.microsoft.com/en-us/dotnet/api/system.random?view=netcore-3.1
CONSTRUCTORS
Random() Initializes a new instance of the Random class
using a default seed value.
Random(Int32) Initializes a new instance of the Random class, using
the specified seed value.
For count_ids As Integer = 0 To 999
A For loop is not appropriate for this problem. We only want to increment the counter if we get a unique ID. The above For loop will increment on every iteration.
Do While Counter < 1000
'Code here
Loop
Notice in my code the counter is only incremented if the ID is unique.
The following loop should work fine but above this code we need to reset strID to an empty string. Otherwise we will have a very long string.
For count_chars As Integer = 0 To 7
strID += strChar(rand.Next(0, 62))
Next count_chars
You should not update the user interface (the label) on each iteration of the loop. Repainting the screen is one of the slowest operations in code. This line will overwrite the string in the label on every iteration.
lblRandomId.Text = strID
Move the update of the UI to after both loops are complete
Your code never checks for duplicates.
Now let's fix it.
We use a List(Of T) to accumulate the IDs. The T stands for Type; in our case it is String. A List is like an array only you don't have to know ahead of time how many entries there will be. No ReDim Preserve required.
Moved Dim strID As String = "" to the beginning of the inner loop so we will get a new strID on each iteration of the outer loop.
Changed strID &= strChar(rand.Next(0, 62)). &= instead of +=. In VB.net we use the ampersand to concatenate strings although the plus sign will work. The .Next method of the Random class has an overload that takes 2 Integers. It is inclusive of the first and exclusive of the second which means (0, 62) will return numbers form 0 to 61. Your string with a length of 62 has indexes of 0 to 61.
Next we check for duplicates with the .Contains method of the List class. This method does just what you would expect. We pass the new ID to the method and it returns a Boolean telling if the string is already in the list.
If it is not in the list, we add it to the list and increment the counter. The counter is only incremented if we have a successful add.
Finally we update the user interface by using a method of the String class. the .Join method takes a separator and the list to join. The TextBox must be multiline and have scroll bars.
I changed the names of the controls so I could test it in my testing program.
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
Dim lst As New List(Of String)
Dim strChar As String = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789"
Dim rand As New Random()
Dim counter As Integer
Do While counter < 1000
Dim strID As String = ""
For count_chars = 0 To 7
strID &= strChar(rand.Next(0, 62))
Next
If Not lst.Contains(strID) Then
lst.Add(strID)
counter += 1
End If
Loop
TextBox1.Text = String.Join(vbCrLf, lst)
End Sub
EDIT
The official documentation for this method can be found here.
https://learn.microsoft.com/en-us/dotnet/api/system.string.join?view=netcore-3.1
I know it will be difficult to read but just take a look. Eventually you will be able to understand it and will be using these docs a lot.
String.Join(separator, List(Of String))
The separator is what to put between the strings in the list. In our case that is vbCrLf which is a vb constant for new line. Cr = Carraiage Return and Lf = Line Feed. Other types of collections that contain strings can also use this method.
The method takes each string in the list and adds the separator. After it is done with the list it returns one long string which we display in the TextBox.
I am having a problem where I just can't seem to get it to split or even display the message. The message variable is predefined in another part of my code and I have debugged to make sure that the value comes through. I am trying to get it so that every 100 characters it goes onto a new line and with every message it also goes onto a new line.
y = y - 13
messagearray.AddRange(Message.Split(ChrW(100)))
Dim k = messagearray.Count - 1
Dim messagefin As String
messagefin = ""
While k > -1
messagefin = messagefin + vbCrLf + messagearray(k)
k = k - 1
End While
k = 0
Label1.Text = Label1.Text & vbCrLf & messagefin
Label1.Location = New Point(5, 398 + y)
You can use regular expression. It will create the array of strings where every string contains 100 characters. If the amount of remained characters is less than 100, it will match all of them.
Dim input = New String("A", 310)
Dim mc = Regex.Matches(input, ".{1,100}")
For Each m As Match In mc
'// Do something
MsgBox(m.Value)
Next
You can use LINQ to do that.
When you do a Select you can get the index of the item by including a second parameter. Then group the characters by that index divided by the line length so, the first character has index 0, and 0 \ 100 = 0, all the way up to the hundredth char which has index 99: 99 \ 100 = 0. The next hundred chars have 100 \ 100 = 1 to 199 \ 100 = 1, and so on (\ is the integer division operator in VB.NET).
Dim message = New String("A"c, 100)
message &= New String("B"c, 100)
message &= New String("C"c, 99)
Dim lineLength = 100
Dim q = message.Select(Function(c, i) New With {.Char = c, .Idx = i}).
GroupBy(Function(a) a.Idx \ lineLength).
Select(Function(b) String.Join("", b.Select(Function(d) d.Char)))
TextBox1.AppendText(vbCrLf & String.Join(vbCrLf, q))
It is easy to see how to change the line length because it is in a variable with a meaningful name, for example I set it to 50 to get the output
AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
BBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBB
BBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBB
CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC
CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC
You can use String.SubString to do that. Like this
Dim Message As String = "your message here"
Dim MessageList As New List (Of String)
For i As Integer = 0 To Message.Length Step 100
If (Message.Length < i + 100) Then
MessageList.Add(Message.SubString (i, Message.Length - i)
Exit For
Else
MessageList.Add(Message.SubString (i, 100))
End If
Next
Dim k = MessageList.Count - 1
...
Here is what your code produced with a bit of clean up. I ignored the new position of the label.
Private Sub OpCode()
Dim messagearray As New List(Of String) 'I guessed that messagearray was a List(Of T)
messagearray.AddRange(Message.Split(ChrW(100))) 'ChrW(100) is lowercase d
Dim k = messagearray.Count - 1
Dim messagefin As String
messagefin = ""
While k > -1
messagefin = messagefin + vbCrLf + messagearray(k)
k = k - 1
End While
k = 0 'Why reset k? It falls out of scope at End Sub
Label1.Text = Label1.Text & vbCrLf & messagefin
End Sub
I am not sure why you think that splitting a string by lowercase d would have anything to do with getting 100 characters. As you can see the code reversed the order of the list items. It also added a blank line between the existing text in the label (In this case Label1) and the new text.
To accomplish your goal, I first created a List(Of String) to store the chunks. The For loop starts at the beginning of the input string and keeps going to the end increasing by 10 on each iteration.
To avoid an index out of range which would happen at the end. Say, we only had 6 characters left from start index. If we tried to retrieve 10 characters we would have an index out of range.
At the end we join the elements of the string with the separated of new line.
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
BreakInto10CharacterChunks("The quick brown fox jumped over the lazy dogs.")
End Sub
Private Sub BreakInto10CharacterChunks(input As String)
Dim output As New List(Of String)
Dim chunk As String
For StartIndex = 0 To input.Length Step 10
If StartIndex + 10 > input.Length Then
chunk = input.Substring(StartIndex, input.Length - StartIndex)
Else
chunk = input.Substring(StartIndex, 10)
End If
output.Add(chunk)
Next
Label1.Text &= vbCrLf & String.Join(vbCrLf, output)
End Sub
Be sure to look up String.SubString and String.Join to fully understand how these methods work.
https://learn.microsoft.com/en-us/dotnet/api/system.string.substring?view=netframework-4.8
and https://learn.microsoft.com/en-us/dotnet/api/system.string.join?view=netframework-4.8
Have to create a lottery program, getting the random numbers and such easily enough. However I'm stumped. Essentially I have 2 buttons. One to display a checked list box with numbers 1-100, along with the 5 lotto numbers. I have a 2nd button that checks 2 things, to make sure that more than 5 numbers are not checked matching numbers. I'm lost on how to check for a match between the selected numbers between the RNG numbers.
Public Class Form1
Private Sub displayBtn_Click(sender As Object, e As EventArgs) Handles displayBtn.Click
Dim lottoNumbers(5) As Integer
Dim counter As Integer = 0
Dim number As Integer
Dim randomGenerator As New Random(Now.Millisecond)
'This will randomly select 5 unique numbers'
Do While counter < 5
number = randomGenerator.Next(0, 98)
If Array.IndexOf(lottoNumbers, number) = -1 Then
lottoNumbers(counter) = number
counter += 1
End If
Loop
'Display the lottery numbers in the label.'
Label1.Text = String.Empty
Array.Sort(lottoNumbers)
For Each num As Integer In lottoNumbers
Label2.Text = "Lottery Numbers"
Label1.Text &= CStr(num) & " "
Next num
For x = 0 To 98
CheckedListBox1.Items.Add(x + 1)
Next
End Sub
Private Sub checkBtn_Click(sender As Object, e As EventArgs) Handles checkBtn.Click
Dim count As Integer = 0
Dim x As Integer
'Checks to see if user checked more than 5'
For x = 0 To CheckedListBox1.Items.Count - 1
If (CheckedListBox1.CheckedItems.Count > 5) Then
MessageBox.Show("You cannot select more than 5 numbers.")
Return
Else
If (CheckedListBox1.GetItemChecked(x) = True) Then
count = count + 1
ListBox1.Items.Add(CheckedListBox1.Items(x))
End If
End If
Next
End Sub
Module Module1
Sub MoveLeft()
Console.WriteLine("You Moved Left")
End Sub
Sub MoveRight()
Dim Number As String
Console.WriteLine("You Moved Right")
Randomize()
Number = Int(Rnd() * 10) + 1
If Number = 1 To 2 Then
Console.WriteLine(" An Enemy Appeared")
ElseIf
Console.WriteLine(" The Way Is Clear")
End If
End Sub
Sub Shoot()
Console.WriteLine("Pew")
End Sub
Sub Main()
Dim quit As Boolean = False
Dim key As String = ""
Do While quit = False
If Console.KeyAvailable Then
key = Console.ReadKey(0).Key
If key = 81 Then
quit = True
End If
Select Case key
Case 37
MoveLeft()
Case 39
MoveRight()
Case 32
Shoot()
End Select
End If
Loop
End Sub
End Module
How do I Get A random Number To roll and make certain values make an enemy appear and other values not.
Instead of
Randomize()
Number = Int(Rnd() * 10) + 1
If Number = 1 To 2 Then
Console.WriteLine(" An Enemy Appeared")
ElseIf
End If
Try
Dim rnd As New Random
Select Case rnd.Next(5)
Case 1
Console.WriteLine(" An Enemy Appeared")
Case Else
Console.WriteLine(" The Way Is Clear")
End Select
This code creates a new randomized randomnumber generator called rnd, generates a random number between 1 and 5 inclusive and if the random number is 1 then an enemy appears. If the random number is anything else, the way is clear.
You only need a range of 5 and a check to see if the result is 1 as this is the same as a range of 10 and checking for a result of 1 or 2
Although speed of computation isn't too important in your program, I think that using a Select Case statement may be quicker than your original code - and is more maintainable later on
' Initialize the random-number generator.
Randomize()
' Generate random value between 1 and 10.
Dim number As Integer = CInt(Int((10 * Rnd()) + 1))
' Show enemy if the integer number is smaller than 3 (= 1, 2)
If number < 3 Then
'your method here to have enemy appear
Else
Console.WriteLine(" The Way Is Clear")
End If
I'm trying to loop this array 100 times (gets a number from 0-99,999). I've tried it several different ways with no luck. I've got it set up so you click a button and it generates the array. The user will then enter a number and hit the other button to check how many times that number shows up in the group of a 100 numbers. Any thoughts how to fix it? I'm stuck.
Dim i As Integer
Dim rnd As New Random()
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnEnter.Click
Dim num As Integer
If Int32.TryParse(txtEnter.Text, num) AndAlso num >= 0 AndAlso num < 10 Then
lblNumber.Text = i.ToString()
Dim counts = From c In i.ToString()
Group By c Into Group
Select DigitGroup = New With {.Count = Group.Count(), .Digit = c, .Group = Group}
Order By DigitGroup.Count Descending, DigitGroup.Digit
Dim numCount = counts.FirstOrDefault(Function(grp) grp.Digit.ToString() = num.ToString())
If numCount IsNot Nothing Then
Dim numMessage = String.Format("There are {0} number {1}'s found.", numCount.Count, num)
MessageBox.Show(numMessage)
Else
MessageBox.Show("Your number does not contain a " & num)
End If
Else
MessageBox.Show("Please enter a number between 0 and 9.")
End If
End Sub
Private Sub btnGetNumber_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnGetNumber.Click
btnEnter.Enabled = True
i = 0
Do Until i > 100
Dim randomInt = rnd.Next(0, 100000)
i = i + 1
i = rnd.Next(0, 100000)
Loop
End Sub
End Class
First of all, it is common to use For Loops when you know the number of loops.
Secondly, you forgot to increment i in the until loop
Finally, you don't need to redeclare rnd in every loop. Something like that sounds better to me :
Dim rnd As New Random()
For i = 1 To 100
Dim randomInt = rnd.Next( 0 , 100000 )
Next
Move the New Random() out of that loop. Make it global and create the instance just one time.
(The Random generator starts using a seed obtained from the current time. Declaring a Random variable inside a loop result in the same seed used again and again. This gives back the same number defeating the randomness of the function) It is like: http://xkcd.com/221/
See another explanation here
Of course, if you don't increment the variable i used to control the loop, you will loop forever
Dim i As Integer
Dim rnd As New Random()
.....
i = 0
Do Until i > 100
Dim randomInt = rnd.Next(0, 100000)
i = i + 1
Loop
Said that, now I can't get what are you trying to do here. There is no array to check and you do not use the value obtained from the Random generator, simply, your i variable exits with value 101.
Now I am just guessing what are your intentions, but perhaps you want just this?
i = rnd.Next(0, 100000)
This will give to the variable i a random number and your subsequent code checks how many, of the required digit, are present in i
I see that you are not adding the variable "i" to increment:
i = 1
Do Until i > 100
Dim rnd As New Random()
Dim randomInt = rnd.Next(0, 100000)
i+=1 'Increment value of i by 1, same as i = i + 1
Loop
The variable of "i" will always be 1 if not incremented. Check that and let me know if that solves the problem!