Leetcode 166 Solution

class Solution {
public:
    string fractionToDecimal(int numerator, int denominator) {
        bool sign = false;

        if ((numerator > 0 && denominator < 0) || (numerator < 0 && denominator > 0))
            sign = true;

        int64_t numerator2 = abs((int64_t)numerator);
        int64_t denominator2 = abs((int64_t)denominator);

        int64_t base = (int64_t)numerator2 / (int64_t)denominator2;
        int64_t next = (int64_t)numerator2 % (int64_t)denominator2;

        string fraction;
        map<int64_t, int> last_pos;
        int loop_start = -1;

        while (next)
        {
            if (last_pos.find(next) != last_pos.end())
            {
                loop_start = last_pos[next];
                break;
            }

            last_pos[next] = fraction.size();
            fraction.push_back(next * 10 / denominator2 + '0');

            next = (next * 10) % denominator2;
        }

        string res = (sign ? "-" : "") + to_string(base);

        if (fraction.size())
        {
            if (loop_start == -1)
            {
                res = res + "." + fraction;
            }
            else
            {
                res = res + "." + fraction.substr(0, loop_start) + "(" + fraction.substr(loop_start) + ")";
            }
        }

        return res;
    }
};