leetcode：Roman to Integer

class Solution {public:    int romanToInt(string s) {         int map[128];        if(s.size()==0)            return 0;        map['I']=1;        map['V']=5;        map['X']=10;        map['L']=50;        map['C']=100;        map['D']=500;        map['M']=1000;        int res = map[s[0]];        for(int i=1;i<s.size();i++)        {            if(map[s[i]]<=map[s[i-1]])                res += map[s[i]];            else                res = res-2*map[s[i-1]]+map[s[i]];        }        return res;    }};