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.

For example,

• Given numerator = 1, denominator = 2, return "0.5".
• Given numerator = 2, denominator = 1, return "2".
• Given numerator = 2, denominator = 3, return "0.(6)".

题目含义：计算两个数的除法，出现无限循环位置时，用括号括起来

1     public String fractionToDecimal(int numerator, int denominator) { 2         if (denominator ==0) return ""; 3         StringBuilder result = new StringBuilder(); 4         String sign = (numerator < 0 == denominator < 0 || numerator == 0) ? "" : "-"; 5         long num = Math.abs((long) numerator); 6         long den = Math.abs((long) denominator); 7         result.append(sign); 8         result.append(num / den); 9         long remainder = num % den;10         if (remainder == 0)11             return result.toString();12         result.append(".");13         HashMap
     
       hashMap = new HashMap
      
       ();14         while (!hashMap.containsKey(remainder)) {15             hashMap.put(remainder, result.length());16             result.append(10 * remainder / den);17             remainder = 10 * remainder % den;18         }19         int index = hashMap.get(remainder);20         result.insert(index, "(");21         result.append(")");22         return result.toString().replace("(0)", "");        23     }