Re: Too many arrays! My head is exploding!

On Tue, May 29, 2012 at 10:55 AM, Tedd Sperling <tedd@sperling.com> wrote: > On 29 May 2012 18:15, Gary <listgj-phpgeneral@yahoo.co.uk> wrote: > >> Okay, let's assume I have three "things", A, B, and C. I need to produce >> an array with a list of all possible combinations of them, however many >> there might be in those combinations: e.g. A, B, C, D, AB, AC, AD, BC, >> ABC (not sure if I've missed any!). Normally I'm pretty good at working >> this stuff out, but to be honest I'm struggling with this one, at least >> to do it in any kind of elegant way. Does anyone have any ideas? > > Sure, but what you are asking for is a permutation and not a combination. His example seems to suggest order does not matter (I've omitted 'D', which I suspect was a typo given the set of A, B, and C): A B C AB AC BC ABC If order did matter, he would have included BA, etc. That all said, combinations typically involve a consistent number of choices, and his example includes various ranges of r. These would be combinations for r = 1: A B C These would be combinations for r = 2: AB AC BC This would be the combination for r = 3: ABC What it seems like he's after is the power set of set ABC (minus the empty set): http://en.wikipedia.org/wiki/Power_set Adam -- Nephtali:  A simple, flexible, fast, and security-focused PHP framework http://nephtaliproject.com