Java for LeetCode 166 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)".
解题思路：

测试中会出现各种临界值，因此，需要先将 numerator 和 denominator转为long，然后计算出整数部分，对于小数部分，将numerator*10后处理，一方面将计算除后的值放到一个list中，另一方面将新的分子放到map里，由于新分子肯定小于denominator，所以肯定会出现0或者重复（因此分数要么有限，要么是无限循环小数）一旦新分母重复出现，意味着结果会出现循环值，将其按照规则写出来即可，JAVA实现如下：

    public String fractionToDecimal(int numerator, int denominator) {
		StringBuilder sb = new StringBuilder();
		if (numerator < 0 && denominator > 0)
			sb.append("-");
		else if (numerator > 0 && denominator < 0)
			sb.append("-");
		Long Lnumerator = (long) numerator;
		if (Lnumerator < 0)
			Lnumerator = -Lnumerator;
		Long Ldenominator = (long) denominator;
		if (Ldenominator < 0)
			Ldenominator = -Ldenominator;
		if (Lnumerator % Ldenominator == 0){
			sb.append(Lnumerator / Ldenominator);
			return sb.toString();
		}
		sb.append(Lnumerator / Ldenominator + ".");
		System.out.println(Lnumerator);
		Lnumerator %= Ldenominator;
		System.out.println(Lnumerator);
		HashMap<Long, Integer> map = new HashMap<Long, Integer>();
		ArrayList<Integer> list = new ArrayList<Integer>();
		map.put(Lnumerator, 0);
		while (true) {
			Lnumerator *= 10;
			while (Lnumerator < Ldenominator) {
				list.add(0);
				map.put(Lnumerator, list.size());
				Lnumerator *= 10;
			}
			list.add((int) (Lnumerator / Ldenominator));
			Lnumerator %= Ldenominator;
			if (Lnumerator == 0) {
				for (int i = 0; i < list.size(); i++)
					sb.append(list.get(i));
				return sb.toString();
			} else if (map.containsKey(Lnumerator)) {
				for (int i = 0; i < map.get(Lnumerator); i++)
					sb.append(list.get(i));
				sb.append("(");
				for (int i = map.get(Lnumerator); i < list.size(); i++)
					sb.append(list.get(i));
				sb.append(")");
				return sb.toString();
			}
			map.put(Lnumerator, list.size());
		}
    }