10进制数字向0~3999的罗马数字的转换

class Solution {
public:
    string intToRoman(int num) {
        char* c[4][10] = {
            { "","I","II","III","IV","V","VI","VII","VIII","IX" },
            { "","X","XX","XXX","XL","L","LX","LXX","LXXX","XC" },
            { "","C","CC","CCC","CD","D","DC","DCC","DCCC","CM" },
            { "","M","MM","MMM" }
        };
        string roman;
        roman.append(c[3][num / 1000 % 10]);
        roman.append(c[2][num / 100 % 10]);
        roman.append(c[1][num / 10 % 10]);
        roman.append(c[0][num % 10]);

        return roman;
    }
};

int main() {
    int n;
    cin >> n;
    Solution s;
    cout << s.intToRoman(n) << endl;
    return 0;
}