in reply to Re: Random Hash Key according to key frequency
in thread Random Hash Key according to key frequency

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;
}

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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.

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Re^3: Random Hash Key according to key frequency
by adrianh (Chancellor) on Dec 04, 2002 at 18:43 UTC
    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]
Re: Re: Re: Random Hash Key according to key frequency
by jdporter (Paladin) on Dec 04, 2002 at 18:42 UTC
[reply]

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