Fraction to Recurring Decimal

class Solution {
public:
    string fractionToDecimal(int numerator, int denominator) {
        if (numerator == 0) return "0";
        string ans;
        long long num = numerator, den = denominator;
        if ((num < 0) ^ (den < 0)) ans.push_back('-');
        num = abs(num); den = abs(den);
        ans += to_string(num / den);
        long long rem = num % den;
        if (rem == 0) return ans;
        ans.push_back('.');
        unordered_map<long long, int> seen;
        while (rem != 0) {
            auto it = seen.find(rem);
            if (it != seen.end()) {
                ans.insert(it->second, "(");
                ans.push_back(')');
                break;
            }
            seen[rem] = ans.size();
            rem *= 10;
            ans += to_string(rem / den);
            rem %= den;
        }
        return ans;
    }
};

import (
    "strconv"
    "strings"
)

func fractionToDecimal(numerator int, denominator int) string {
    if numerator == 0 {
        return "0"
    }
    var sb strings.Builder
    num := int64(numerator)
    den := int64(denominator)
    if (num < 0) != (den < 0) {
        sb.WriteByte('-')
    }
    if num < 0 {
        num = -num
    }
    if den < 0 {
        den = -den
    }
    sb.WriteString(strconv.FormatInt(num/den, 10))
    rem := num % den
    if rem == 0 {
        return sb.String()
    }
    sb.WriteByte('.')
    seen := map[int64]int{}
    ans := sb.String()
    for rem != 0 {
        if pos, ok := seen[rem]; ok {
            return ans[:pos] + "(" + ans[pos:] + ")"
        }
        seen[rem] = len(ans)
        rem *= 10
        ans += strconv.FormatInt(rem/den, 10)
        rem %= den
    }
    return ans
}

class Solution:
    def fractionToDecimal(self, numerator: int, denominator: int) -> str:
        if numerator == 0:
            return "0"
        parts = []
        if (numerator < 0) ^ (denominator < 0):
            parts.append('-')
        num, den = abs(numerator), abs(denominator)
        parts.append(str(num // den))
        rem = num % den
        if rem == 0:
            return ''.join(parts)
        parts.append('.')
        seen = {}
        frac = []
        while rem != 0:
            if rem in seen:
                idx = seen[rem]
                frac.insert(idx, '(')
                frac.append(')')
                break
            seen[rem] = len(frac)
            rem *= 10
            frac.append(str(rem // den))
            rem %= den
        return ''.join(parts) + ''.join(frac)

var fractionToDecimal = function(numerator, denominator) {
    if (numerator === 0) return "0";
    const parts = [];
    if ((numerator < 0) !== (denominator < 0)) parts.push('-');
    let num = Math.abs(numerator), den = Math.abs(denominator);
    parts.push(String(Math.floor(num / den)));
    let rem = num % den;
    if (rem === 0) return parts.join('');
    parts.push('.');
    const seen = new Map();
    let frac = '';
    while (rem !== 0) {
        if (seen.has(rem)) {
            const idx = seen.get(rem);
            frac = frac.slice(0, idx) + '(' + frac.slice(idx) + ')';
            break;
        }
        seen.set(rem, frac.length);
        rem *= 10;
        frac += String(Math.floor(rem / den));
        rem %= den;
    }
    return parts.join('') + frac;
};

class Solution {
    public String fractionToDecimal(int numerator, int denominator) {
        if (numerator == 0) return "0";
        StringBuilder ans = new StringBuilder();
        long num = numerator, den = denominator;
        if ((num < 0) ^ (den < 0)) ans.append('-');
        num = Math.abs(num);
        den = Math.abs(den);
        ans.append(num / den);
        long rem = num % den;
        if (rem == 0) return ans.toString();
        ans.append('.');
        Map<Long, Integer> seen = new HashMap<>();
        while (rem != 0) {
            if (seen.containsKey(rem)) {
                int pos = seen.get(rem);
                ans.insert(pos, '(');
                ans.append(')');
                break;
            }
            seen.put(rem, ans.length());
            rem *= 10;
            ans.append(rem / den);
            rem %= den;
        }
        return ans.toString();
    }
}

function fractionToDecimal(numerator: number, denominator: number): string {
    if (numerator === 0) return "0";
    const parts: string[] = [];
    if ((numerator < 0) !== (denominator < 0)) parts.push('-');
    let num = Math.abs(numerator), den = Math.abs(denominator);
    parts.push(String(Math.floor(num / den)));
    let rem = num % den;
    if (rem === 0) return parts.join('');
    parts.push('.');
    const seen = new Map<number, number>();
    let frac = '';
    while (rem !== 0) {
        if (seen.has(rem)) {
            const idx = seen.get(rem)!;
            frac = frac.slice(0, idx) + '(' + frac.slice(idx) + ')';
            break;
        }
        seen.set(rem, frac.length);
        rem *= 10;
        frac += String(Math.floor(rem / den));
        rem %= den;
    }
    return parts.join('') + frac;
}