Random numbers with no duplicates

[chad3006]

I'm having some issues getting a program to list some random numbers with no duplicate numbers.  It's really a sorting program, I guess.  The following is a stripped down version of the program which will randomize 10 numbers, but I'll eventually need to sort almost 2000 numbers.  I can successfully identify the duplicates, but when I try to re-randomize it seems to still include duplicates. 

[START]

   cls
   a = 0
   c = 0
   qtyfiles = 10
   dim check$(qtyfiles)
   cls
[NEWARRAY]

   for c = 1 to qtyfiles
   GOSUB [RANDOMIZER]
   print check$(c)
   next c
   print

[CHECKER]

   for c = 1 to qtyfiles
   for a = 1 to qtyfiles
   if check$(c) = check$(a) then
   if c <> a then   ' TO ELLIMINATE CHECKING NUMBER AGAINST ITSELF
   print "y"; " "; check$(c); " "; check$(a)
'   GOSUB [RANDOMIZER]
'   GOTO [CHECKER]
   else
   end if
   else
   print "n"; " "; check$(c); " "; check$(a)
   end if
   next a
   print "***********"
   next c

[END]
'   print
'   for c = 1 to qtyfiles
'   print check$(c)
'   next c
  end

[RANDOMIZER]
   number$ = str$(int(rnd(qtyfiles)*qtyfiles) + 1)
   check$(c) = number$
   RETURN

[Rod]

So do you want to shuffle a defined set of numbers. So numbers 1-100 shuffled randomly with no duplicates, just 1-100 in random order?

[chad3006]

The big picture is this:  I need to read a directory of files, then rename them randomly with a number for their name.  I've got the rename and directory reading  figured out.

Yes, it would be a bit like shuffling cards...except for more than 52.

[Walt Decker]

That is like "how long would it take 1000 monkeys to with McBeth?" Answer, never.

The very nature of randomness is to expect duplicates given a large enough sample.

What you should do is put the numbers in an array, sort the array and eliminate duplicates, then run your generator again.

[klewlis]

you could load your numbers into an array, then randomly shuffle them, here is one such example.




   qtyfiles = 100

   dim filename$(qtyfiles)

   for a = 1 to qtyfiles
       filename$(a) = str$(a) + ".dat" 'or whatever extension you need.
   next a

   for a = 1 to 100
       print a;
       print space$(5);
       print "filename$("; a; ") = "; filename$(a)
   next a

   for a = 1 to (qtyfiles * 100)
       i = int(rnd(1) * qtyfiles) + 1
       tempvar$ = filename$(i)
       j = int(rnd(1) * qtyfiles) + 1
       filename$(i) = filename$(j)
       filename$(j) = tempvar$
   next a

   for a = 1 to qtyfiles
       print a;
       print space$(5);
       print "filename$("; a; ") = "; filename$(a)
   next a

   wait

   end


then rename your files using the array in numerical order.

[Rod]

You need an array, a two column array. The first column is the file name the second is str$(rnd(0)) Then sort the array on column 2 now you have the array in random order so work the array from top to bottom renaming the file as you go from 1-n

Sort is well enough described in the help file let’s assume you have the file names in filename$() and n is the number of file names.


Dim a$(n,2)
For i = 1 to n
a$(i,1)=filename$(i)
a$(i,2)=str$(rnd(0))
Next
Sort a$(,1,n,2

[mknarr]

What I do is have an array of 100 elements, generate a random number. lets say the number is 67, Check the array number 67 to see if there is a 1 in it. If there is a one, generate another number. If not,put a 1 in element #67 and use the number.