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)".

 

这题很麻烦。

1。首先要判断符号， numberator 和 denominator 都是可正可负的。

2。numberator 要用long 否则会溢出。

3。每一次只能被减数*10，而且当没有出现小数点前，不会出现括号。所以先把整数部分和小数点全部输出，

 1 public class Solution {

 2     public String fractionToDecimal(int numerator, int denominator) {

 3         if(numerator == 0) return new String("0");

 4         StringBuilder sb = new StringBuilder();

 5         boolean o = (numerator < 0) ^ (denominator < 0);

 6         if(o) sb.append("-");

 7         long a = Math.abs((long)numerator);

 8         long b = Math.abs((long)denominator);

 9         sb.append(String.valueOf(a / b));

10         a = a % b;

11         if(a == 0) return sb.toString();

12         sb.append(".");

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

14         for(int pos = sb.length(); a != 0; pos ++){

15             a *= 10;

16             if(map.containsKey(a)){

17                 sb.insert(map.get(a), "(");

18                 sb.append(")");

19                 break;

20             }

21             sb.append((int)(a / b));

22             map.put(a, pos);

23             a = a % b;

24         }

25         return sb.toString();

26     }

27 }