My basic idea is to map the array indices to bits in a binary number. If a bit is on, you take that element out of the source array. For example:
0 = 0b0000 --> {nothing}
3 = 0b0011 --> 'horse:cow'
13 = 0b1101 --> 'horse:dog:cat'
The algorithm then simply becomes a loop over 1 .. 2**@kw -1, testing the bits for each number.
Here's my first implementation of it. It's probably not as efficient as possible yet.
sub rhesa {
# initial source in sequence order
my $source = 'horse:cow:dog:cat';
my @kw = split /:/, $source;
my @res;
for my $i( 1 .. 2**@kw - 1 ) {
my @ar; my $t;
while( $i > 0 ) {
push @ar, $kw[$t] if $i & 1;
$i >>= 1; $t++;
}
push @res, join ':', @ar;
}
return @res;
}
I'm a bit irritated with the number of temporary variables, but I can't think of anything prettier just now. Hope it helps :)
BTW, a simple Benchmark comparison showed a 200% speed increase over your version.
-
Are you posting in the right place? Check out Where do I post X? to know for sure.
-
Posts may use any of the Perl Monks Approved HTML tags. Currently these include the following:
<code> <a> <b> <big>
<blockquote> <br /> <dd>
<dl> <dt> <em> <font>
<h1> <h2> <h3> <h4>
<h5> <h6> <hr /> <i>
<li> <nbsp> <ol> <p>
<small> <strike> <strong>
<sub> <sup> <table>
<td> <th> <tr> <tt>
<u> <ul>
-
Snippets of code should be wrapped in
<code> tags not
<pre> tags. In fact, <pre>
tags should generally be avoided. If they must
be used, extreme care should be
taken to ensure that their contents do not
have long lines (<70 chars), in order to prevent
horizontal scrolling (and possible janitor
intervention).
-
Want more info? How to link
or How to display code and escape characters
are good places to start.
|