166. Fraction to Recurring Decimal.java

// 166. Fraction to Recurring Decimal

class Solution {
    public String fractionToDecimal(int numerator, int denominator) {
       if (numerator == 0 || denominator == 0) {
            return "0";
        }
        
        StringBuilder sb = new StringBuilder();
        if (numerator < 0 && denominator > 0 || numerator > 0 && denominator < 0) { // to find number is negative or bot
            sb.append("-");
        }
        
        long num = Math.abs((long) numerator);
        long denom = Math.abs((long) denominator);
        long remainder = num % denom;
        sb.append(num/denom);
        
        if (remainder == 0) {
            return sb.toString();
        }
        
        sb.append(".");
        Map<Long, Integer> map = new HashMap<>();
        while (remainder != 0) {
            if (map.containsKey(remainder)) { // once you see the same remainder then you know it's going to start recurring 
                sb.insert(map.get(remainder), "(");
                sb.append(")");
                break;                    
            } 
            
            map.put(remainder, sb.length());
            remainder *= 10;
            sb.append(remainder/denom);
            remainder = remainder % denom;
        }
        
        return sb.toString();
    }
}