Random Numbers

I've got a small app that generates random numbers, but I don't want it to select the same number twice.

Can anyone help out with code.

Cheers.

Then your not really talking about a Random number if it can't pick the same one twice ;)


But honestly. What you need to do is make a list for each of the numbers you have to choose from.

If you decide the random number can be from 1 to 100 then you need to be able to keep track of 100 numbers in a list!!!!

But here is a sneaky solution that you might find quite interesting... It is probably slightly LESS memory intensive than other solutions but a tiny bit heavier on the processing side, but it DOES avoid the need for arrays, collections and the like (which get tiresome)

Code:

---

' Set up the Variables
Dim sNumbers as String    ' Keeps track of what you have used
Dim iMaxNumber as Integer  ' Highest number possible
Dim iNum as Integer        ' Iteration through your set
Dim iRand as Integer      ' The number picked this time around
Dim sMsg as String        ' Used to return the list

iMaxNumber = 100

sNumbers = String("0",iMaxNumber) ' Clear the list

For iNum = 1 to 10  ' Generate 10 random numbers
  iRand = Int(Rnd * iMaxNumber)+1      ' Have a guess
  Do While Mid(sNumbers,iRand,1) <> "0" ' If you already picked it
    iRand = Int(Rnd * iMaxNumber)+1    ' Pick again
  Loop                                  ' Keep doing it until you get a new one

  Mid(sNumbers,iRand,1) = "1"          ' Mark this number off as being used

  sMsg = sMsg & "- Random Number (" & iNum & ") = " & iRand & vbCR ' Add it to the list

Next iNum

MsgBox "Your Random Numbers : " & vbCR & vbCR & sMsg

---

But don't forget to reset the list all back to "0" again before using it a second time (unless you want to still pick new ones). Also remember that the more numbers you have chosen the slower it will be in finding another one you haven't chosen.

The alternative to speed this up is to create a collection with all the numbers in it as members and as you select the remaining members to delete that one... but it takes more space.

Ah what the heck... here is the collection one as well :

Code:

---

Dim cNumbers as New Collection
Dim iMaxNumber as Integer
Dim iNum as Integer
Dim iRand as Integer
Dim sMsg as String

iMaxNumber = 100

For iNum = 1 to iMaxNumber
  cNumbers.Add iNum
Next iNum

For iNum = 1 to 10 ' Still picking 10 numbers
  If cNumbers.Count > 0 Then
    iRand = Int(Rnd * cNumbers.Count) + 1
    sMsg = sMsg & "- Random Number (" & iNum & ") = " & cNumbers(iRand)
 
    cNumbers(iRand).Remove
  End If
Next iNum

MsgBox "Random Numbers : " & vbCR & vbCR & sMsg

---

Now with this one you can keep pulling out numbers until the collection is reduced to nothing, it will work just as fast for the first number as it will for the last number but it takes a WHOLE lot more memory and the more numbers you want to choose from the more memory it will use.

Your choice ;P

I'll give it a go. Thanks.