http://qs321.pair.com?node_id=242835


in reply to Weighted random numbers generator

After typing this up, I see Zaxo already posted the same idea. Ah well, here it is anyway.
#!/usr/bin/perl use strict; # Assign a weight to each item. In this example # pigs get twice the weight of dogs or cows my %weight = ( "dog" => 1, "cow" => 1, "pig" => 2 ); # Create an array with a number of elements # equal to the weights of the items my @bucket; foreach my $animal (keys %weight) { push @bucket, ($animal) x $weight{$animal}; } # @bucket now looks like this: # # $bucket[0] = "dog" # $bucket[1] = "cow" # $bucket[2] = "pig" # $bucket[3] = "pig" # # "pig" has twice as many slots as "dog" or "cow" # The choose_weighted() subroutine now just has to # pick a random element from the array. sub choose_weighted { my $bucket = shift; return $bucket->[rand(@$bucket)]; } # Test code to demonstrate it works my %count; for (1..1000) { my $animal = &choose_weighted(\@bucket); $count{$animal}++; } foreach my $animal (keys %count) { print "$animal: $count{$animal}\n"; }

-Matt