[LeetCode] Fraction to Recurring Decimal

[LeetCode] Fraction to Recurring Decimal

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 )".

  
  

  This problem is still difficult to implement. We need to consider the input of negative numbers, especially the Boundary Value of the integer type-2147483648. The simplest way is to convert all input values to positive numbers of long integers.

  In addition, because we want to record the cyclic part of the decimal point, we also need to use a Map to record each decimal point and the corresponding remainder value. If the same remainder value is met, it indicates that the part of the Start loop is encountered.

  public String fractionToDecimal(int numerator, int denominator) {long longNumerator = Math.abs((long) numerator);long longDenominator = Math.abs((long) denominator);StringBuilder sb = new StringBuilder();if ((long) numerator * denominator < 0) sb.append("-");sb.append(longNumerator / longDenominator);long remainder = longNumerator % longDenominator;if (remainder == 0) return sb.toString();sb.append(".");StringBuilder fracSb = new StringBuilder();Map
     
       map = new HashMap
      
       ();int index = 0;while (remainder != 0) {remainder *= 10;long nextRemainder = remainder % longDenominator;// If repeated part occurs.if (map.containsKey(remainder)) {fracSb.insert(map.get(remainder), "(");fracSb.append(")");break;}map.put(remainder, index++);fracSb.append(remainder / longDenominator);remainder = nextRemainder;}sb.append(fracSb);return sb.toString();}