roman-to-integer.cpp

class Solution {
public:
int num(char c) {
           if (c == 'I') {
               return 1;
           }
           if (c == 'V') {
               return 5;
           }
           if (c == 'X') {
               return 10;
           }
           if (c == 'L') {
               return 50;
           }
           if (c == 'C') {
               return 100;
           }
           if (c == 'D') {
               return 500;
           }
           if (c == 'M') {
               return 1000;
           }
           return 0;
       }
   int romanToInt(string s) {
       
       int sum = 0;
       int index = 0;
       int n = s.size();
       while (index < n-1) {

           if (num(s[index]) >= num(s[index + 1])) {
               sum += num(s[index]);
               index++;
           } else  {
               sum -= num(s[index]);
               index++;
           }
       }
       sum += num(s[index]);
       return sum;
   }
};