in reply to Random Hash Key according to key frequency

  my @thresh;
  my $total = 0;
  for ( keys %hash )
  {
    $total += $hash{$_};
    push @thresh, [ $total, $_ ];
  }

  my $string;
  for ( 1 .. 30 )
  {
    my $r = rand $total;
    my $i = 0;
    while ( $r > $thresh[$i][0] ) { $i++; }
    $string .= $thresh[$i][1];
  }

[download]

jdporter
...porque es dificil estar guapo y blanco.

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Re: Re: Random Hash Key according to key frequency
by iburrell (Chaplain) on Dec 04, 2002 at 18:38 UTC
    It is possible to do it without constructing the threshold array by stepping through the hash a second time. 
    my $total = 0;
foreach my $key (keys %hash) {
    $total += $hash->{$key};
}

my $r = int(rand($total));

my $sum = 0;
foreach my $key (keys %$hash) {
    $sum += $hash->{$key};
    if ($r < $sum) 
        return $key;
}

    [download]
    It might be possible to do only one pass through the hash using a technique like finding a random line from a file when the number of lines in the file isn't known.
[reply]
[d/l]
      It might be possible to do only one pass through the hash using a technique like finding a random line from a file when the number of lines in the file isn't known.

      What... like this :-)

      sub random_key {
    my $hash = shift;
    my $line = 0;
    my $match = undef;
    while (my ($key, $value) = each %$hash) {
        $match = $key if rand($line += $value) < $value;
    };
    return($match);
};

      [download]

      Update: removed unnecessary inner loop.

[reply]
[d/l]
[reply]

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