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Postings from March 2002
Jenda Krynicky wrote:
>
> From: "Mahendra Thacker" <mnt_cal@snet.net>
> >
> > # Cash5 Lotto: draw of 6 unique non-zero numbers from 1..35
> >
> > my $top = 36; # rand gives a rand numb less than top, hence
> > my @myarr = ();
> > my $myrand;
> >
> > while ( @myarr < 6 ) {
> > $myrand = rand $top;
> > $myrand %= 35;
> > next if $myrand =~ 0;
> > $t = join ' ', @myarr;
> > next if $t =~ $myrand;
> > push @myarr, $myrand;
> > }
> > print join ' ', @myarr;
>
> You have a bug in there. This would never give you 35. Keep in
^^^^^
More than one. :-) "$t =~ $myrand" should be "$t == $myrand"
> mind that ($x modulo 35) is a number between 0 and 34 (inclusive).
>
> If you want a random number from 1..35 you should do this:
>
> $randnum = 1 + int(rand 35);
>
> And if you want 6 unique :
>
> my @myarr;
> { # this block is here just to restrict the availability
> # of %seen
> my %seen;
> while (@myarr < 6) {
> my $num = 1 + int(rand 35);
> push @myarr, $num
> unless $seen{$num}++
> }
> }
>
> if you wanted that a bit longer:
>
> my @myarr;
> { # this block is here just to restrict the availability
> # of %seen
> my %seen;
> while (@myarr < 6) {
> my $num = 1 + int(rand 35);
> if (! $seen{$num}) {
> push @myarr, $num;
> $seen{$num} = 1
> }
> }
> }
Because of the nature of "randomness" this algorithm could take a long
time to run. Better to shuffle an array of 35 numbers and pick six.
my @myarr = ( 1 .. 35 );
for ( my $i = @myarr; --$i; ) {
my $j = int rand( $i + 1 );
next if $i == $j;
@myarr[ $i, $j ] = @myarr[ $j, $i ];
}
@myarr = splice @myarr, rand( @myarr - 6 ), 6;
print "@myarr\n";
John
--
use Perl;
program
fulfillment
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