public class Solution {

     public String fractionToDecimal(int numerator, int denominator) {

         long num = numerator, den = denominator;

         if (num ==  || den == ) return "";

         boolean negative = (num >  && den < ) || (num <  && den > );

         num = Math.abs(num);

         den = Math.abs(den);

         String integ = (negative ? "-" : "") + String.valueOf(num / den);

         num = num % den;

         if (num != ) {

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

             int pos = ;

             StringBuilder frac = new StringBuilder();

             while (num != ) {

                 map.put(num, pos);

                 num = num * ;

                 frac.append(num / den);

                 num = num % den;

                 if (map.containsKey(num)) {

                     // 将非循环部分和循环部分分开

                     String pre = frac.substring(, map.get(num));

                     String loop = frac.substring(map.get(num));

                     return integ + "." + pre + "(" + loop + ")";

                 }

                 pos++;

             }

             return integ + "." + frac.toString();

         }

         return integ;

     }

 }