class Solution {
    public String fractionToDecimal(int numerator, int denominator) {
        // 轉(zhuǎn) long 計(jì)算，防止溢出
        long a = numerator, b = denominator;
        // 如果本身能夠整除，直接返回計(jì)算結(jié)果
        if (a % b == 0) return String.valueOf(a / b);
        StringBuilder sb = new StringBuilder();
        // 如果其一為負(fù)數(shù)，先追加負(fù)號(hào)
        if (a * b < 0) sb.append('-');
        a = Math.abs(a); b = Math.abs(b);
        // 計(jì)算小數(shù)點(diǎn)前的部分，并將余數(shù)賦值給 a
        sb.append(String.valueOf(a / b) + ".");
        a %= b;
        Map<Long, Integer> map = new HashMap<>();
        while (a != 0) {
            // 記錄當(dāng)前余數(shù)所在答案的位置，并繼續(xù)模擬除法運(yùn)算
            map.put(a, sb.length());
            a *= 10;
            sb.append(a / b);
            a %= b;
            // 如果當(dāng)前余數(shù)之前出現(xiàn)過(guò)，則將 [出現(xiàn)位置 到 當(dāng)前位置] 的部分摳出來(lái)（循環(huán)小數(shù)部分）
            if (map.containsKey(a)) {
                int u = map.get(a);
                return String.format("%s(%s)", sb.substring(0, u), sb.substring(u));
            }
        }
        return sb.toString();
    }
}

func fractionToDecimal(numerator, denominator int) string {
    if numerator%denominator == 0 {
        return strconv.Itoa(numerator / denominator)
    }

    s := []byte{}
    if numerator < 0 != (denominator < 0) {
        s = append(s, '-')
    }

    // 整數(shù)部分
    numerator = abs(numerator)
    denominator = abs(denominator)
    integerPart := numerator / denominator
    s = append(s, strconv.Itoa(integerPart)...)
    s = append(s, '.')

    // 小數(shù)部分
    indexMap := map[int]int{}
    remainder := numerator % denominator
    for remainder != 0 && indexMap[remainder] == 0 {
        indexMap[remainder] = len(s)
        remainder *= 10
        s = append(s, '0'+byte(remainder/denominator))
        remainder %= denominator
    }
    if remainder > 0 { // 有循環(huán)節(jié)
        insertIndex := indexMap[remainder]
        s = append(s[:insertIndex], append([]byte{'('}, s[insertIndex:]...)...)
        s = append(s, ')')
    }

    return string(s)
}

func abs(x int) int {
    if x < 0 {
        return -x
    }
    return x
}