q3.rb

#this code borrowed from the internet
class Array
  # Returns the "power set" for this Array. This means that an array with all
  # subsets of the array's elements will be returned.
  def power
    # the power set line is stolen from http://johncarrino.net/blog/2006/08/11/powerset-in-ruby/
    inject([[]]) do |c,y|
      r=[]
      c.each do |i|
        r<<i
        r<<i+[y]
        end
      r
    end
  end
end

#end borrowed section




 @nums = [3, 4, 9, 14, 15, 19, 28, 37, 47, 50, 54, 56, 59, 61, 70, 73, 78, 81, 92, 95, 97, 99]




@count = 0

puts "BEFORE POWERSET"
all_sets = @nums.power
puts "AFTER POWERSET"

i = 0
puts "sets to process: #{all_sets.size}"
all_sets.each do |subset|

  if i % 20 == 0
    puts "DEBUG: processing subset #{i} of #{all_sets.size}:  #{i.to_f / all_sets.size}% complete"
  end
  
  subset.sort!
  max = subset.pop


  @count += 1 if max == subset.inject(0){|sum,item| sum+item}

  i += 1

  
end


puts "count: #{@count}"