1 class Solution { 2 public: 3     int romanToInt(string s) { 4         if (s.empty()) return 0; 5          6         int result = 0; 7         int n = s.size(); 8         unordered_map<char, int> roman; 9         roman[‘I‘] = 1;10         roman[‘V‘] = 5;11         roman[‘X‘] = 10;12         roman[‘L‘] = 50;13         roman[‘C‘] = 100;14         roman[‘D‘] = 500;15         roman[‘M‘] = 1000;16         17         for (int i = 0; i < n; i++) {18             if (i < n - 1) {19                 if (s[i] == ‘I‘ && s[i + 1] == ‘V‘) {result += 4; i++;}20                 else if (s[i] == ‘I‘ && s[i + 1] == ‘X‘) {result += 9; i++;}21                 else if (s[i] == ‘X‘ && s[i + 1] == ‘L‘) {result += 40; i++;}22                 else if (s[i] == ‘X‘ && s[i + 1] == ‘C‘) {result += 90; i++;}23                 else if (s[i] == ‘C‘ && s[i + 1] == ‘D‘) {result += 400; i++;}24                 else if (s[i] == ‘C‘ && s[i + 1] == ‘M‘) {result += 900; i++;}25                 else result += roman[s[i]];26             }27             else {28                 result += roman[s[i]];29             }30         }31         return result;32     }33 };