class Solution {public:    int romanToInt(string s)     {        std::unordered_map
     
       hm;        hm['M'] = 1000;        hm['D'] = 500;        hm['C'] = 100;        hm['L'] = 50;        hm['X'] = 10;        hm['V'] = 5;        hm['I'] = 1;                        int i = 0, len = s.length(), ret = 0;        while(i < len)        {            char c = s[i];            if(i < len - 1 && hm[s[i + 1]] > hm[s[i]])            {                ret += hm[s[i + 1]] - hm[s[i]];                i ++;            }            else            {                ret += hm[s[i]];            }            i ++;        }        return ret;    }};