Re: Lotto simulation

[Simon Wright <simon@pushface.org>]

montgrimpulo <aghte@hotlinemail.com> writes:

> A workaround would be to test in each round, if that number has
> already been selected.  However, the probability would not be the same
> as with a reduced set as the selection would be always from the full
> set.

This seems perfectly reasonable.

If you think of numbered balls like the UK lottery, and after each pick
replace the picked ball by one without a number.  By the time you get to
the last 2 numbered balls, each of them has a 50% chance of being the
one that's eventually picked, no matter how many times you discard
unnumbered balls. Depending on the RNG, of course.

Another possibility: create an array of {ball-number, random-float},
sort by the random-float component, choose the first N entries.