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Given a roman numeral, convert it to an integer.

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

这里说一下罗马数的简单规则，左边的数>右边的数时，两个数相加，左边的数<右边的数时，右边的数减去左边的数，如

"DCXXI"  ＝  621

romanToint = {'I':1,'V':5,'X':10,'L':50,'C':100,'D':500,'M':1000}  ＃罗马数与整数之间的转换关系

class Solution(object):    def romanToInt(self, s):        """        :type s: str        :rtype: int        """        romanToint = {'I':1,'V':5,'X':10,'L':50,'C':100,'D':500,'M':1000}        xlength = len(s)        results = 0        for a in range(1,xlength):            if romanToint[s[a]]>romanToint[s[a-1]]:                results = results-romanToint[s[a-1]]            else:                results = results+romanToint[s[a-1]]        results = results+romanToint[s[-1]]        return results

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