166. Fraction to Recurring Decimal

Given two integers representing the numerator and denominator of a fraction, return the fraction in string format.

If the fractional part is repeating, enclose the repeating part in parentheses.

If multiple answers are possible, return any of them.

It is guaranteed that the length of the answer string is less than 104 for all the given inputs.

struct DecimalNumber{
    string decimal;
    optional<int> repeatedRemainder;

    DecimalNumber(string decimal, optional<int> repeatedRemainder) : decimal(decimal), repeatedRemainder(repeatedRemainder) {}
};
class Solution {
private:
    string stringToNum(long num) {
        string ret;
        if (num == 0) { return "0"; }
        long N = num, rev, count = 0;
        rev = N;
        while ((rev % 10) == 0) { count++; rev /= 10;} //obtain the count of the number of 0s
        rev = 0;
        while (N != 0) { rev = (rev<<3) + (rev<<1) + N % 10; N /= 10;}  //store reverse of N in rev
        while (rev != 0) { ret += (rev % 10 | 0b110000); rev /= 10;}
        while (count--) ret += '0';

        return ret;
    }

    string getDecimalNumber(long numerator, long denominator) {
        if(numerator == 0)
            return "";
        set<pair<long, long>> remainder;
        return "." + calculateDecimalNumber(numerator * 10, denominator, remainder).decimal;
    }

    DecimalNumber calculateDecimalNumber(long numerator, long denominator, set<pair<long, long>> &remainder) {
        if(numerator == 0)
            return DecimalNumber("", std::nullopt);
        int quotient = numerator / denominator;
        numerator %= denominator;
        if(remainder.find(make_pair(numerator + denominator * quotient, numerator)) != remainder.end()) {
            return DecimalNumber(")", numerator);
        }

        remainder.insert(make_pair(numerator + denominator * quotient, numerator));
        auto decimalNumber = calculateDecimalNumber(numerator * 10, denominator, remainder);
        return decimalNumber.repeatedRemainder.value_or(-1) == numerator ?
        DecimalNumber("(" + stringToNum(quotient) + decimalNumber.decimal, std::nullopt) :
        DecimalNumber(stringToNum(quotient) + decimalNumber.decimal, decimalNumber.repeatedRemainder);
    }
public:
    string fractionToDecimal(int numerator, int denominator) {
        string solution = (numerator < 0 && denominator > 0) || (numerator > 0 && denominator < 0) ? "-" : "";
        long n = numerator <= 0 ? (long)(numerator) * -1 : numerator;
        long d = denominator <= 0 ? (long)(denominator) * -1 : denominator;

        solution += stringToNum(n / d);
        n %= d;

        return solution + getDecimalNumber(n, d);
    }
};