Fraction to Recurring Decimal

class Solution {
public:
    string fractionToString(int num, int denom) {
        if (num == 0) {
            return "0";
        }
        string result;
        // Check for negative result
        if (num < 0 ^ denom < 0) {
            result += "-";
        }
        // Avoid overflow issues
        long long numerator = llabs((long long)num);
        long long denominator = llabs((long long)denom);
        result += to_string(numerator / denominator);
        long long rem = numerator % denominator;
        if (rem == 0) {
            return result;
        }
        result += ".";
        unordered_map<long long, int> record;
        while (rem != 0) {
            if (record.count(rem)) {
                result.insert(record[rem], "(");
                result += ")";
                break;
            }
            record[rem] = result.length();
            rem *= 10;
            result += to_string(rem / denominator);
            rem %= denominator;
        }
        return result;
    }
};

To convert a fraction to its decimal form where the decimal might recur, you can use a C++ function that effectively handles different cases including zero, positives, and negatives, as well as repeating decimals. Here is a concise summary of how to implement this based on the provided C++ code:

1. Start by verifying if the numerator is zero. If so, return "0" since any number divided by another (non-zero) number results in zero.

2. Initialize a string to build your result. Check and append a "-" to the result if the fraction result is negative (i.e., if only one of either denominator or numerator is negative).

3. Convert both the numerator and the denominator into positive values using llabs function to avoid overflow and to handle the division and modulus operations properly.

4. Perform integer division of the absolute values of numerator and denominator to fetch the integral part of the result and append it to the result string.

5. Calculate the remainder of the division. If the remainder is zero, return the current result as the division yields a non-recurring decimal.

6. If the remainder is not zero, append a period ('.') to the result string signaling the beginning of the fractional part.

7. Use a hash map to track remainders and their corresponding positions in the result string. This aids in identifying the start of recurring decimals.

8. Multiply the remainder by 10 before dividing by the denominator again to compute the next digit of the fractional part. Continue this process and keep checking whether the current remainder has appeared before in the hash map:

   • If it has, insert an open parenthesis at the recorded position and append a close parenthesis to the end of the result to indicate the beginning and end of the recurring part.
   • Update the remainder and length of the result string accordingly until you find a repeating remainder or the remainder becomes zero.

This approach ensures that all cases are covered, including fractions that result in both recurring and non-recurring decimals. Use the hash map effectively to determine when the digits start to repeat, marking those repetitions accurately in the result string with parentheses.