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，

public class Solution {
    public String fractionToDecimal(int numerator, int denominator) {
        if(numerator == 0) return new String("0");
        StringBuilder sb = new StringBuilder();
        boolean o = (numerator < 0) ^ (denominator < 0);
        if(o) sb.append("-");
        long a = Math.abs((long)numerator);
        long b = Math.abs((long)denominator);
        sb.append(String.valueOf(a / b));
        a = a % b;
        if(a == 0) return sb.toString();
        sb.append(".");
        HashMap<Long, Integer> map = new HashMap<Long, Integer>();
        for(int pos = sb.length(); a != 0; pos ++){
            a *= 10;
            if(map.containsKey(a)){
                sb.insert(map.get(a), "(");
                sb.append(")");
                break;
            }
            sb.append((int)(a / b));
            map.put(a, pos);
            a = a % b;
        }
        return sb.toString();
    }
}