166. Fraction to Recurring Decimal

166. Fraction to Recurring Decimal
There are too many corner cases for this problem when numerator and denominator are Integer.MIN_VALUE, so convert them to long type to avoid taking care of corner cases.
Basically, it will keep calculating reminder until either it equals to 0 or it appears before(repeating decimal). Use hashmap to store the position of the reminder, so when it reappears, we can insert '(' to the right position.

  public String fractionToDecimal(int numerator, int denominator) {  

     boolean neg=(numerator>0 && denominator<0) || (numerator<0 && denominator>0);  
     long numLong=Math.abs((long)numerator);  
     long denomLong=Math.abs((long)denominator);  
     long res=numLong/denomLong;  
     numLong=numLong%denomLong;  
     StringBuilder sb=new StringBuilder();  
     if(neg) sb.append("-");  
     sb.append(Math.abs(res));  
     if(numLong==0) return sb.toString();  
     sb.append('.');  
     HashMap<Long,Integer> used=new HashMap<Long,Integer>();  
     while(numLong!=0 && !used.containsKey(numLong)){  
       used.put(numLong,sb.length());  
       sb.append(numLong*10/denomLong);  
       numLong=numLong*10%denomLong;  
     }  
     if(numLong!=0)  
     {  
      sb.append(")");  
      sb.insert(used.get(numLong),"(");  
     }  
     return sb.toString();  
   }