From: r2d2@... (Niklas Frykholm)
Date: 2001-05-29T13:10:04+09:00
Subject: [ruby-talk:15903] Re: Subsets of a set

>What I need is a method that will allow me to generate all of the
>subsets of a given set
>that are a certain size.

class Array
	def all_subsets(size)
		if size==0
			return [[]]
		else
			prev = all_subsets(size-1)
			res = []
			prev.each do |s|
				self.each do |elem|
					if not s.member?(elem)
						res << s + [elem]
					end
				end
			end
			return res
		end
	end
end

// Niklas