From: swille <sillewille@...>
Date: 2005-10-23T10:52:25+09:00
Subject: Re: combination sums of several arrays

On 10/22/05, David Vincelli <micologist@gmail.com> wrote:
> I'm writing a little BlackJack program for fun and I'm at the point
> where I have to decide which point value to assign to a hand. As you
> know, an Ace may be worth 1 or 11 in this game - whatever is closer to
> 21 without going over.
>
> Considering this, I know I have to come up with an algorithm that
> first determines what the different point values may be (the extreme
> case may be that a player got all four aces, now I'd have to determine
> all combinations of the players cards).
>
> This demonstrates some of the code I wrote:
>
> pl = Player.new
> pl.hand.each { |card|  p pl.card.value }
>
> might produce this output:
> [1, 11]
> [5]
> [10]
>
> For the above example, so what I'm looking for is a method that will
> calculate all possible point totals. For this example  I'd get the
> results [16, 26]
>
> I'm thinking I might do this by first building a binary tree, creating
> unique branches that would add up to the results when I applied some
> recursive algorithm to it. But I'm curious to know how other people
> might do this? (I'm especially curious to see if anyone has some
> solution that does not require building a tree and recursing..).
>
> Thanks,
>
> --
> David Vincelli
>
>

Maybe I'm not understanding what exactly you want, but I think I'd
dump the [1, 10] thing and just count it as [1].  Then maybe something
like:

sum = pl.hand.inject { |sum, n| sum + n }
if pl.hand.include?(1)
    if sum + 10 <= 21
        sum += 10
    end
end

Or did I miss something?