Different numbers from 1 to 10

Question

I want to generate 10 different numbers from a range of 0-9. the desired output may look like this, 9 0 8 6 5 3 2 4 1 7

Dim arraynum(9) As Integer
Dim crmd A         


        

Answer 1

Option Explicit 'Force variable declaration

Private Sub Form_Load()
    Dim Ar(1 To 100) As Integer 'The array to store it in
    Dim i, j As Integer 'Counters for loops
    Dim X As Integer 'Variable to store the random generated number
    Dim bFound As Boolean 'Boolean to check if the value has been generated before

    Randomize 'Just once to ensure that we get random values

    For i = 1 To 100
        Do 'Start the loop that generates a random number and checks if it has already been generated
            X = RandomInteger(1, 100) 'Generate a random number
            bFound = False 'Set the boolean to false, if we find the number while searching the array, we'll set it to true which means that we already have that number
            For j = 1 To i 'We only need to check up to i (since we haven't put any values in the rest of the array)
                If Ar(j) = X Then 'If an item of the arrray is the same as the last generated number
                    bFound = True 'Set the boolean to true (it already exists)
                    DoEvents 'To not freeze until the looping is done
                    Exit For 'Since we found it there is no need to check the rest
                End If
            Next
        Loop Until bFound = False 'If it wasn't found then we'll add it, if it was found then we go back to generating a new number and comparing it with all the items of the array
        Ar(i) = X 'Add it to the array
    Next

    ShowInTextBox Text1, Ar 'Just to print the data and see it
End Sub

Private Function RandomInteger(Lowerbound As Integer, Upperbound As Integer) As Integer 'The random number generator code
    RandomInteger = Int((Upperbound - Lowerbound + 1) * Rnd + Lowerbound)
End Function

Private Sub ShowInTextBox(TB As TextBox, A() As Integer) 'Just a sub to show the data in a textbox
    Dim i As Integer

    TB.Text = ""

    For i = 1 To UBound(A)
        TB.Text = TB.Text & CStr(A(i)) & vbCrLf
    Next

    TB.Text = Left$(TB.Text, Len(TB.Text) - 2)
End Sub

Answer 2

This is the simplest but working code. Also there are no APIs!

Dim a(1 To 10), tmp, count, isRepeated
count = 1
Randomize
While count <= 10
    isRepeated = False
    tmp = Left(Rnd * 10, 1)
    For i = 1 To 10
        If tmp = a(i) Then isRepeated = True: Exit For
    Next
    If isRepeated = False Then a(count) = tmp: count = count + 1
Wend
YourLine = Join(a, "")

Answer 3

Having no performance requirements specified, I would use the below short and simple code:

Randomize
With CreateObject("Scripting.Dictionary")
    Do
        .Item(Int(Rnd * 10)) = ""
    Loop Until .Count = 10
    MsgBox Join(.Keys)
End With

Answer 4

Choosing random values and then throwing away those that you've already used is a bad idea. It makes the run-times longer as the pool of available numbers gets less since you're throwing away more and more.

What you want is a shuffle list which I would implement with the following code (pseudo-code since it's homework):

dim n[10]                 // gives n[0] through n[9]
for each i in 0..9:
    n[i] = i              // initialize them to their indexes
nsize = 10                // starting pool size
do 10 times:
    i = rnd(nsize)        // give a number between 0 and nsize-1
    print n[i]
    nsize = nsize - 1     // these two lines effectively remove the used number
    n[i] = n[nsize]

By simply selecting a random number from the pool then replacing it with the top number from that pool and reducing the size of the pool, you get a shuffle without having to worry about a large number of swaps up front. This is important if the number is high in that it doesn't introduce an unnecessary startup delay.

For example, examine the following bench-check:

<--------- n[x] ---------->
for x = 0 1 2 3 4 5 6 7 8 9  nsize  rnd(nsize)  output
---------------------------  -----  ----------  ------
        0 1 2 3 4 5 6 7 8 9     10           4       4
        0 1 2 3 9 5 6 7 8        9           7       7
        0 1 2 3 9 5 6 8          8           2       2
        0 1 8 3 9 5 6            7           6       6
        0 1 8 3 9 5              6           0       0
        5 1 8 3 9                5           2       8
        5 1 9 3                  4           1       1
        5 3 9                    3           0       5
        9 3                      2           1       3
        9                        1           0       9

You can see the pool reducing as you go and, because you're always replacing the used one with an unused one, you'll never have a repeat.

And now your homework consists of turning that into VB :-)

---

And, since this homework is now almost certainly overdue (about a year ago), I'll post a VBA solution showing how to do it, for completeness.

Option Explicit
Option Base 0
Sub Macro1()
    Randomize
    Dim list(10) As Integer
    Dim i As Integer
    Dim size As Integer
    Dim pos As Integer
    Dim result As String

    For i = 0 To 9
        list(i) = i
    Next

    size = 10
    result = ":"
    For i = 1 To 10
        pos = Int(Rnd() * size)
        result = result & list(pos) & ":"
        size = size - 1
        list(pos) = list(size)
    Next

    MsgBox result
End Sub

This generated, on three separate runs:

:5:7:4:2:9:1:0:8:3:6:
:3:9:6:0:7:8:5:4:2:1:
:7:6:3:5:1:8:9:0:4:2:

Answer 5

you need a random permutation over an array of 0 to 9.

I forgot how to write basic.. something like:

dim a(10)
for i=0 to 9 do a(i) = i
rem do random permute over a:
for i=0 to 9 do 
  j = rand() mod (i+1)
  tmp = a(j)
  a(i) = a(j)
  a(j) = tmp
next i