1 public class Solution {
 2     public int romanToInt(String s) {
 3         int sum = 0;
 4         int[] num = new int[s.length()];
 5         if(s == null) return 0;
 6         for(int i=0; i<s.length(); ++i){
 7             char c = s.charAt(i);
 8             if(c == ‘I‘) num[i] = 1;
 9             if(c == ‘V‘) num[i] = 5;
10             if(c == ‘X‘) num[i] = 10;
11             if(c == ‘L‘) num[i] = 50;
12             if(c == ‘C‘) num[i] = 100;
13             if(c == ‘D‘) num[i] = 500;
14             if(c == ‘M‘) num[i] = 1000;
15         }
16         for(int j=1; j<num.length; ++j){
17             if(num[j] > num[j-1]){
18                 num[j-1] = num[j]-num[j-1];
19                 num[j] = 0;
20                 ++j;
21             }
22         }
23         for(int k=0; k<num.length; ++k){
24             sum = sum + num[k];
25         }
26         return sum;
27     }
28 }

 1 class Solution {
 2 public:
 3     int romanToInt(string s) {
 4         // Start typing your C/C++ solution below
 5         // DO NOT write int main() function
 6         map<char, int> S;
 7         S[‘I‘] = 1;
 8         S[‘V‘] = 5;
 9         S[‘X‘] = 10;
10         S[‘L‘] = 50;
11         S[‘C‘] = 100;
12         S[‘D‘] = 500;
13         S[‘M‘] = 1000;
14         int ret = 0;
15         for (int i = 0; i < s.size(); i++) ret += (i>0 && S[s[i]] > S[s[i-1]])? S[s[i]]-2*S[s[i-1]] : S[s[i]];
16         return ret;
17     }
18 };