CircleHackathonInviteChallenge.rb

# Code to solve the circle hackathon invite challenge http://discovercircle.com/hackathon

def main
  # seven digit number where number is ABCDEFG
  # A*B*C = C*D*E = E*F*G
  # A,B,C,D,E,F,G can't be 0
  # can't use 5 or 7 since they're prime
  
  possible_digits = [1,2,3,4,6,8,9]
  prime_factorization = [[1],[2],[3],[2,2],[2,3],[2,2,2],[3,3]]
  
  prime_factorization.permutation(7).each do |iter|
    val1 = product_of_array(iter[0] + iter[1] + iter[2])
    val2 = product_of_array(iter[2] + iter[3] + iter[4])
    val3 = product_of_array(iter[4] + iter[5] + iter[6])

    if val1 == val2 and val2 == val3
      puts product_of_array(iter[3])
      return
    end
  end
  return nil
end

def product_of_array(arr)
  return arr.reduce(1) do |product, value|
    product * value
  end
end

if __FILE__ == $PROGRAM_NAME
  main
end