FracToRecStr.java

/*
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.

Example 1:

Input: numerator = 1, denominator = 2
Output: "0.5"
Example 2:

Input: numerator = 2, denominator = 1
Output: "2"
Example 3:

Input: numerator = 2, denominator = 3
Output: "0.(6)"

*/

   public String fractionToDecimal(int numerator, int denominator) {
    if (numerator == 0) {
        return "0";
    }
    StringBuilder fraction = new StringBuilder();
    // If either one is negative (not both)
    if (numerator < 0 ^ denominator < 0) {
        fraction.append("-");
    }
    // Convert to Long or else abs(-2147483648) overflows
    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();
    }
    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();
}