[Leetcode] Roman to Integer

Given a roman numeral, convert it to an integer.

Input is guaranteed to be within the range from 1 to 3999.

纯模拟，规则见：Integer to Roman。

class Solution {
public:
    map<char, int> roman;
    void init() {
        roman['I'] = 1;
        roman['V'] = 5;
        roman['X'] = 10;
        roman['L'] = 50;
        roman['C'] = 100;
        roman['D'] = 500;
        roman['M'] = 1000;
    }
    
    bool check(char a, char b) {
        return roman[a] < roman[b];
    }
    
    int romanToInt(string s) {
        init();
        int res = 0;
        for (int i = 0; i < s.length(); ++i) {
            if (i > 0 && check(s[i-1], s[i])) {
                res -= 2 * roman[s[i-1]];
            }
            res += roman[s[i]];
        }
        return res;
    }
};