public class Solution {

    public String fractionToDecimal(int numerator, int denominator) {

        if (numerator == 0) {

            return "0";

        }

        StringBuilder res = new StringBuilder();

        // "+" or "-"

        res.append(((numerator > 0) ^ (denominator > 0)) ? "-" : "");

        long num = Math.abs((long)numerator);

        long den = Math.abs((long)denominator);

        // integral part

        res.append(num / den);

        num %= den;

        if (num == 0) {

            return res.toString();

        }

        // fractional part

        res.append(".");

        HashMap<Long, Integer> map = new HashMap<Long, Integer>();

        map.put(num, res.length());

        while (num != 0) {

            num *= 10;

            res.append(num / den);

            num %= den;

            if (map.containsKey(num)) {

                int index = map.get(num);

                res.insert(index, "(");

                res.append(")");

                break;

            }

            else {

                map.put(num, res.length());

            }

        }

        return res.toString();

    }

}

class Solution(object):

    def fractionToDecimal(self, numerator, denominator):

        """

        :type numerator: int

        :type denominator: int

        :rtype: str

        """

        result = ""

        if (numerator > 0 and denominator < 0) or (numerator < 0 and denominator > 0):

            result = "-"

        dvd, dvs = abs(numerator), abs(denominator)

        result += str(dvd / dvs)

        dvd %= dvs

        if dvd > 0:

            result += "."

        lookup = {}

        while dvd and dvd not in lookup:

            lookup[dvd] = len(result)

            dvd *= 10

            result += str(dvd / dvs)

            dvd %= dvs

        if dvd in lookup:

            result = result[:lookup[dvd]] + "(" + result[lookup[dvd]:] + ")"

        return result

// upgraded parameter types

string fractionToDecimal(int64_t n, int64_t d) {

    // zero numerator

    if (n == 0) return "0";

    string res;

    // determine the sign

    if (n < 0 ^ d < 0) res += '-';

    // remove sign of operands

    n = abs(n), d = abs(d);

    // append integral part

    res += to_string(n / d);

    // in case no fractional part

    if (n % d == 0) return res;

    res += '.';

    unordered_map<int, int> map;

    // simulate the division process

    for (int64_t r = n % d; r; r %= d) {

        // meet a known remainder

        // so we reach the end of the repeating part

        if (map.count(r) > 0) {

            res.insert(map[r], 1, '(');

            res += ')';

            break;

        }

        // the remainder is first seen

        // remember the current position for it

        map[r] = res.size();

        r *= 10;

        // append the quotient digit

        res += to_string(r / d);

    }

    return res;

}