Roman to Interger

Given a roman numeral, convert it to an integer.

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

class Solution {public:    int romanToInt(string s) {        map<char, int> roman;        roman['I'] = 1;        roman['X'] = 10;        roman['C'] = 100;        roman['M'] = 1000;        roman['V'] = 5;        roman['L'] = 50;        roman['D'] = 500;        int len = s.size();        int sum = roman[s[len-1]];        //cout << sum << endl;        char cur = s[len-1];        for (int i=len-2; i>=0; i--) {            if (roman[s[i]] >= roman[cur]) {                sum += roman[s[i]];            } else {                sum -= roman[s[i]];            }            //cout << sum << endl;            cur = s[i];        }          return sum;    }};