roman-to-integer

#include <list>

class Solution
{
public:

    list<int> t;

    int sumchar(char c)
    {
        switch (c)
        {
            case 'I':
                return 1;
            case 'V':
                return 5;
            case 'X':
                return 10;
            case 'L':
                return 50;
            case 'C':
                return 100;
            case 'D':
                return 500;
            case 'M':
                return 1000;
        }
        return 0;
    };

    int romanToInt(string s)
    {
        for (int i = 0; i < s.size(); i++)
        {
            int r = sumchar(s[i]);
            if (t.empty())
                t.push_back(r);
            else
            {
                if (t.back() < r)
                {
                    int sum = 0;
                    while ((!t.empty()) && (t.back() < r))
                    {
                        sum += t.back();
                        t.pop_back();
                    }
                    t.push_back(r - sum);
                }
                else
                {
                    t.push_back(r);
                }
            }
        }

        return std::accumulate(t.begin(), t.end(), 0);
    }
};