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Re: removing the goto

by TilRMan (Friar)
on Jun 03, 2007 at 06:05 UTC ( #618960=note: print w/ replies, xml ) Need Help??


in reply to removing the goto

redo LABEL is the answer to your question, but here are a couple of "better" ways to select $maxclients unique elements from a bag (@weighteddiv).

This approach has the advantage of being simple, but it is relatively slow for large datasets and does not preserve the order in which the numbers were picked:

my @weighteddiv = (('1234') x 7, ('9876') x 42, ('1123') x 13); my %selected; my $maxclients = 2; until (keys %selected == $maxclients or @weighteddiv == 0) { my $i = rand(+@weighteddiv); # Not $# my $pluck = splice @weighteddiv, $i, 1; ++$selected{$pluck}; } my @selected = keys %selected; print "Selected: @selected\n";

You can preserve the order with a little more code in the loop to create @selected incrementally:

if (++$selected{$pluck} == 1) { push @selected, $pluck; }

Finally, a complicated but efficient solution involving probabilities:

my @weighteddiv = (('1234') x 7, ('9876') x 42, ('1123') x 13); my @selected; my $maxclients = 2; my %occurrence; foreach (@weighteddiv) { $occurrence{$_}++; } my $total = @weighteddiv; until (@selected == $maxclients or keys %occurrence == 0) { my $i = rand($total); keys %occurrence; # reset hash iterator while (my ($value, $count) = each %occurrence) { if ($i < $count) { push @selected, $value; delete $occurrence{$value}; $total -= $count; last; } $i -= $count; } } print "Selected: @selected\n";

Caveat: All solutions untested.


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