class Solution { public: int romanToInt(string s) { if (s.size() == 0) return 0; map<char, int> mp; mp['I'] = 1; mp['V'] = 5; mp['X'] = 10; mp['L'] = 50; mp['C'] = 100; mp['D'] = 500; mp['M'] = 1000; int len = s.size(); int sum = mp[s[len⑴]]; for (int i = len⑵; i >= 0; i--) { if (mp[s[i]] < mp[s[i+1]]) sum -= mp[s[i]]; else sum += mp[s[i]]; } return sum; } };