powerset.rb

Powerset of a set is all possible sets from that set: i.e. imaging you have a 1/0 for each element indicating on off. Then size is 2^N
def powerset(arr)
  partial = []
  pwr_helper(arr, partial, 0)
end
def pwr_helper(arr, partial, n)
  if(n >= arr.size)
    puts partial.inspect
    return
  end
  partial.push(arr[n])
  pwr_helper(arr, partial, n+1)
  partial.pop
  pwr_helper(arr,partial,n+1)
end
powerset([1,2])
powerset([1,2,3])