3月3日(5) Roman to Integer

class Solution {
public:
    int romanToInt(string s) {
        int ret = 0;
        int last_t = 0;
        
        for (int i = s.length()-1; i>=0; --i)
        {
            int t;
            switch(s[i])
            {
                case ‘I‘:
                    t = 1;
                    break;
                case ‘V‘:
                    t = 5;
                    break;
                case ‘X‘:
                    t = 10;
                    break;
                case ‘L‘:
                    t = 50;
                    break;
                case ‘C‘:
                    t = 100;
                    break;
                case ‘D‘:
                    t = 500;
                    break;
                case ‘M‘:
                    t = 1000;
                    break;
                default:
                    t = 0;
            }
            if (last_t <= t)
            {
                ret += t;
            } 
            else {
                ret -= t;
            }
            last_t = t;
        }
        return ret;
    }
};