LeetCode166:分数到循环小数的转换

class Solution {    public String fractionToDecimal(int numerator, int denominator) {        if (numerator == 0) return "0";        if (numerator == Integer.MAX_VALUE && denominator == -1) return String.valueOf((double)numerator / (double)denominator);        long num = (long)numerator;        long den = (long)denominator;        boolean positive = true;        if (num * den <0) positive = false;        num = Math.abs(num);        den = Math.abs(den);        String pre = String.valueOf(num / den);        if (!positive) pre = '-' + pre;        long remain = num % den;        if (remain == 0) return pre;        HashMap m = new HashMap<>();        StringBuilder str = new StringBuilder();        int index = 0;        while (remain != 0 && !m.containsKey(remain)) {            str.append(String.valueOf((remain * 10) / den));            m.put(remain, index++);            remain = (remain * 10) % den;        }        if (remain == 0) return pre + '.' + str.toString();        else {            str.insert((int)m.get(remain), '(');            str.append(')');            return pre + '.' + str.toString();        }    }}