LeetCode: Roman to Integer

class Solution {
public:
    int romanToInt(string s) {
        int map[26];
        char romanChar[] = { ‘I‘, ‘V‘, ‘X‘, ‘L‘, ‘C‘, ‘D‘, ‘M‘ };
        map[‘I‘ - ‘A‘] = 1;
        map[‘V‘ - ‘A‘] = 5;
        map[‘X‘ - ‘A‘] = 10;
        map[‘L‘ - ‘A‘] = 50;
        map[‘C‘ - ‘A‘] = 100;
        map[‘D‘ - ‘A‘] = 500;
        map[‘M‘ - ‘A‘] = 1000;
        int res = 0, tmp = 0;
        for (int i = 0; i < s.size(); i++)
        {
            if (map[s[i] - ‘A‘] > tmp)
            {
                res = res + map[s[i] - ‘A‘] - tmp * 2;
                
            }
            else
            {
                res = res + map[s[i] - ‘A‘];
            }
            tmp = map[s[i] - ‘A‘];
        }
        return res;
    }
};