166. Fraction to Recurring Decimal

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166. Fraction to Recurring Decimal

Description

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.

If multiple answers are possible, return any of them .

It is guaranteed that the length of the answer string is less than 10^4 for all the given inputs.

Example 1:

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Input: numerator = 1, denominator = 2
Output: "0.5"

Example 2:

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Input: numerator = 2, denominator = 1
Output: "2"

Example 3:

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Input: numerator = 4, denominator = 333
Output: "0.(012)"

Constraints:

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

Hints/Notes

Solution

Language: C++

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class Solution {
public:
    string fractionToDecimal(int numerator, int denominator) {
        if (numerator == 0) {
            return "0";
        }
        string res;
        if (numerator < 0 ^ denominator < 0) {
            res.push_back('-');
        }
        long dividend = labs(numerator);
        long divisor = labs(denominator);
        res.append(to_string(dividend / divisor));
        if (dividend % divisor == 0) {
            return res;
        }
        dividend = dividend % divisor;
        unordered_map<int, int> previous;
        res.push_back('.');
        int digits = 1;
        while (dividend != 0) {
            if (previous.contains(dividend)) {
                res.insert(previous[dividend], "(");
                res.push_back(')');
                return res;
            }
            previous[dividend] = res.size();
            dividend *= 10;
            res.append(to_string(dividend / divisor));
            dividend %= divisor;
        }
        return res;
    }
};