[rails-oceania] Re: Algorithm Problem

Tue, 31 Mar 2009 14:08:41 -0700

I think Mark's answer was correct given the example you initially gave. However, if you want to iterate over groups of dissimilar sets without hard coding the looping to a fixed 'n' then I think you're after something like a multi-dimension iterator.


I'm pretty sure I have one for Ruby somewhere too.

The basic mechanism in my implementation is just like a car's odometer, but instead of each set of digits being the digits 0-9 they can vary to be sets of anything. When the least significant set overflows, it increments the set to it's right to increment by one, and if that overflows, then it tells the set to it's right to increment, etc.

I think if you imagine how a car odometer works you'll understand my code pretty quickly.

Good luck!

Alex Pooley (ABN: 47 643 918 301)
Freelance Developer

Mobile: 0438 313 337
Address:
  PO Box 17,
  Applecross, 6953
  Western Australia


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On 31/03/2009, at 9:53 PM, Torm3nt wrote:


Unfortunately it doesn't quite work that straight forward when the
number of the different option groups = n =P


On Wed, Apr 1, 2009 at 12:52 AM, Mark Ratjens

Hmm ... what idioms are we allowed then? :-)

Iterate over the sizes
   within each size
      iterate over the colours
         make a combination and stow it somewhere

Does that make sense?

Either that or get some sleep :-)

Torm3nt wrote:
This may seem rather simple to some, but being late at night it's
driving me up the wall..

The context behind this is I'm trying to create all unique product
options for a product.

Consider:

We have two product option groups, size and colour.

Size contains: S, M, L, XL
Colour contains: red, blue, green, black, brown

I need to write an algorithm (this isn't for ruby btw, so no ruby
idioms =P), that gets all unique combinations, for example:

S red, S blue, S green, S black, S brown
M red, M blue.etc.etc.

They're all valid, but I can't then go:

red S - it's exactly the same option as before.

I have tried to do this three different ways and each way I've hit a daed end.


HELP!

=)









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