Re: [android-developers] How to generate unique Random Numbers between 1 to 9

Ah, sure, sure, that's true. I guess the broader point is that
there's no reason to artificially impose the constraint that numbers
can't be repeated: in fact it hurts you in terms of security..

Kris

On Wed, Jun 19, 2013 at 8:43 AM, Michael Banzon <michael@banzon.dk> wrote:
> My point was simply that if you want me to select a random number, but
> hands me of list of numbers I'm not allowed to pick, it can't really
> be random. If you limit the length of the number (this is programming
> - there is always a limit) there is a maximum of how many "random"
> numbers I can give you ;-)
>
> On Wed, Jun 19, 2013 at 2:25 PM, Kristopher Micinski
> <krismicinski@gmail.com> wrote:
>> That's not true, it can still be random: just over a different state
>> space. (In particular [0-9]^n \ {alpha^n | any character is repeated
>> in alpha})
>>
>> OP: you could pull out a statistics book and read about random events,
>> how to generate them using coins, etc... But the easiest way is to
>> generate a random number, add it to the list if it's not already in
>> the list, etc... The uniformity argument works based on the invariant
>> that at each stage the next number you choose to "fix" the rest of
>> your choices is random, hence the distribution remains random.
>>
>> # let assemble_random_nums len =
>> let rand () = (Random.int 9) + 1 in
>> let rec h l = function
>> | 0 -> l
>> | i -> let r = rand () in if (List.mem r l) then (h l i) else (h
>> (r::l) (i-1))
>> in
>> h [] len;;
>> val assemble_random_nums : int -> int list = <fun>
>> # assemble_random_nums 4;;
>> - : int list = [1; 8; 3; 9]
>> # assemble_random_nums 4;;
>> - : int list = [2; 9; 5; 4]
>> # assemble_random_nums 4;;
>>
>> Kris
>>
>> On Wed, Jun 19, 2013 at 7:03 AM, Michael Banzon <michael@banzon.dk> wrote:
>>> First: This isn't really a question related to Android development.
>>>
>>> Second: Random unique numbers between 1 and 9 (including both
>>> extremes) is a set of 9 numbers (I really hope that we are talking
>>> about integers and not real/floating point numbers).
>>>
>>> Third: If you request a unique sequence of numbers 1 to 9 it can't be
>>> random as it would include a check for uniqueness that would remove
>>> some degree of randomness.
>>>
>>> On Wed, Jun 19, 2013 at 11:56 AM, vamshi ch <vamshi0408@gmail.com> wrote:
>>>> Hi All,
>>>>
>>>> In my application i want to generate random numbers between 1 to 9 and
>>>> that is unique. once i get the random number that should not be repeated for
>>>> any one, any where and for me also. it's similar to OTP(one time password)
>>>> but some time OTP will be repeated and that is alphanumerical but in my case
>>>> that should not be happen and i need numbers only.
>>>>
>>>> Please can you tell me what is the approach to achieve it. Please help out
>>>> of this..
>>>>
>>>>
>>>> Please share the code if you have any regarding this..
>>>>
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>>>
>>>
>>>
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>
>
>
> --
> Michael Banzon
> http://michaelbanzon.com/
>
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