Roman to Integer

 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 };