166. 分数到小数

给定两个整数，分别表示分数的分子 numerator 和分母 denominator，以 字符串形式返回小数 。

如果小数部分为循环小数，则将循环的部分括在括号内。

如果存在多个答案，只需返回 任意一个 。

对于所有给定的输入，保证 答案字符串的长度小于 104 。

示例 1：

输入：numerator = 1, denominator = 2
输出："0.5"

示例 2：

输入：numerator = 2, denominator = 1
输出："2"

示例 3：

输入：numerator = 2, denominator = 3
输出："0.(6)"

示例 4：

输入：numerator = 4, denominator = 333
输出："0.(012)"

示例 5：

输入：numerator = 1, denominator = 5
输出："0.2"

提示：

• -2^31 <= numerator, denominator <= 2^31 – 1
• denominator != 0

Python 解答：

class Solution:
    def fractionToDecimal(self, numerator: int, denominator: int) -> str:
        adic = {}
        index = 0
        is_posivite = True
        if (numerator > 0 and denominator < 0) or (numerator < 0 and denominator > 0):
            is_posivite = False
        numerator, denominator = abs(numerator), abs(denominator)

        interger = numerator//denominator
        remainder = numerator % denominator
        pre = str(interger)
        if not is_posivite:
            pre = '-' + pre
        if remainder > 0:
            pre += '.'

        nex = []
        is_repeated = -1
        while remainder > 0:

            if remainder not in adic.keys():
                adic[remainder] = index
                index += 1
            else:
                is_repeated = adic[remainder]
                break

            numerator =  remainder*10
            interger, remainder = divmod(numerator, denominator)
            nex.append(str(interger))

            if len(nex)+len(pre) >= 10**4:
                break

        result = ''
        if is_repeated != -1:
            nex.insert(is_repeated, '(' )
            result = pre+''.join(nex)+')'
        else:
            result = pre+''.join(nex)
        return result