$solutions = 0
$numbers = []
$flags = []

def find_solutions(k, target_sum)
  if target_sum == 0
    # found a solution!
    (0..$numbers.length).each { |i| if ($flags[i]) then print $numbers[i], " "; end }
    print "\n"
    $solutions = $solutions + 1
  else
    if k < $numbers.length
      if target_sum >= $numbers[k]
        $flags[k] = true
        find_solutions k+1, target_sum-$numbers[k]
        $flags[k] = false
      end
      find_solutions k+1, target_sum
    end
  end
end

def find_subset_sum(target_sum)
  print "\nNow listing all subsets which sum up to ", target_sum, ":\n"
  $solutions = 0
  (0..$numbers.length()).each { |i| $flags[i] = false }
  find_solutions 0, target_sum
  print "Found ", $solutions, " different solutions.\n"
end

def subset_sum_test(size)
  total = 0
  target_sum = 0
  (0..size).each { |i| $numbers[i] = rand(1000); total += $numbers[i]; print $numbers[i], " " }
  target_sum = total/2
  find_subset_sum target_sum
end

subset_sum_test 40