Grokking #223

class Solution {
    public String fractionToDecimal(int numerator, int denominator) {
        // Edge case: numerator is 0
        if (numerator == 0) {
            return "0";
        }

        StringBuilder fraction = new StringBuilder();
        // If numerator and denominator have the different sign
        if (numerator < 0 ^ denominator < 0) {
            fraction.append("-");
        }

        // integral part
        long dividend = Math.abs(Long.valueOf(numerator));
        long divisor = Math.abs(Long.valueOf(denominator));
        fraction.append(String.valueOf(dividend / divisor));

        long remainder = dividend % divisor;
        if (remainder == 0) {
            return fraction.toString();
        }

        // fractional part
        fraction.append(".");
        Map<Long, Integer> map = new HashMap<>();
        while (remainder != 0) {
            if (map.containsKey(remainder)) {
                fraction.insert(map.get(remainder), "(");
                fraction.append(")");
                break;
            }

            map.put(remainder, fraction.length());
            remainder *= 10;
            fraction.append(String.valueOf(remainder / divisor));
            remainder %= divisor;
        }

        return fraction.toString();
    }
}