gistfile1.txt

def solution(roman)
  numerals = Hash[ 'X' => 10, 'V' => 5, 'I' => 1, 'L' => 50, 'C' => 100, 'D' => 500, 'M' => 1000 ]
	roman_array = roman.scan(/((\w)\2*)/).map(&:first).reverse
  
  decimal_array = roman_array.map { |x|
  	numerals[x[0]]*x.length
  }
 	
  last_num = 0
  decimal_array.map! { |i|
  	if last_num > i then
    	last_num = i
    	i= -i
    else
    	last_num = i
    	i
    end
  }
  answer = decimal_array.reduce(:+) 
  
  return answer
  
end