python-leetcode/roman-to-integer.py at master · mindheist/python-leetcode · GitHub

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#https://leetcode.com/problems/roman-to-integer/
# Given a roman numeral, convert it to an integer.

# Input is guaranteed to be within the range from 1 to 3999.

# Solution
# ========
# (1) The idea is fairly straight forward - Use a dictionary of Key:values ( in which the roman numerals are the Keys and the values are the integer equivalents

# (2) The character string will be parsed from right to left

# (3) the variable "running_value" tracks the result so far

# (4) Keep adding to the result if the romans numbers are in the increasing order

# (5) In case the onder decreases , subtract that value from the result (ie) ex: IV - while parsing from Right to Left I < V , subtract the value of I from V

import unittest
class Solution:
    # @return an integer
    def romanToInt(self, s):
    	# http://en.wikipedia.org/wiki/Roman_numerals

		# I	1
		# V	5
		# X	10
		# L	50
		# C	100
		# D	500
		# M	1,000

		running_value = 0
		previous_value = 0
		romans = { 'I':1 , 'V':5 , 'X':10 , 'L':50 , 'C':100 , 'D':500 ,'M':1000 }
		for i in range(len(s)-1,-1,-1):
			#print s[i]
			if romans[s[i]] < previous_value:
				running_value = running_value - romans[s[i]]
			else:
				running_value = running_value + romans[s[i]]
			previous_value = romans[s[i]]
		return running_value

class TestRomanToInteger(unittest.TestCase):
    my_solution = Solution()

    def test_roman_1(self):
        self.assertEquals(self.my_solution.romanToInt('I'),1)

    def test_roman_V(self):
        self.assertEquals(self.my_solution.romanToInt('V'),5)

    def test_roman_X(self):
        self.assertEquals(self.my_solution.romanToInt('X'),10)

    def test_roman_L(self):
        self.assertEquals(self.my_solution.romanToInt('L'),50)

    def test_roman_C(self):
        self.assertEquals(self.my_solution.romanToInt('C'),100)

    def test_roman_D(self):
        self.assertEquals(self.my_solution.romanToInt('D'),500)

    def test_roman_M(self):
        self.assertEquals(self.my_solution.romanToInt('M'),1000)

    def test_roman_IV(self):
        self.assertEquals(self.my_solution.romanToInt('IV'),4)

    def test_roman_IX(self):
        self.assertEquals(self.my_solution.romanToInt('IX'),9)

    def test_roman_II(self):
        self.assertEquals(self.my_solution.romanToInt('II'),2)


if __name__ == "__main__":
    unittest.main()

# print "XXX =" , my_solution.romanToInt('XXX')
# print "XXXV =" , my_solution.romanToInt('XXXV')
# print "XL = " , my_solution.romanToInt('XL')
# print "MCMXCVI = " , my_solution.romanToInt('MCMXCVI')
# print my_solution.romanToInt('XLIX')