Fraction to Recurring Decimal
<p>Given two integers representing the <code>numerator</code> and <code>denominator</code> of a fraction, return <em>the fraction in string format</em>.</p>

<p>If the fractional part is repeating, enclose the repeating part in parentheses.</p>

<p>If multiple answers are possible, return <strong>any of them</strong>.</p>

<p>It is <strong>guaranteed</strong> that the length of the answer string is less than <code>10<sup>4</sup></code> for all the given inputs.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>

<pre>
<strong>Input:</strong> numerator = 1, denominator = 2
<strong>Output:</strong> &quot;0.5&quot;
</pre>

<p><strong class="example">Example 2:</strong></p>

<pre>
<strong>Input:</strong> numerator = 2, denominator = 1
<strong>Output:</strong> &quot;2&quot;
</pre>

<p><strong class="example">Example 3:</strong></p>

<pre>
<strong>Input:</strong> numerator = 4, denominator = 333
<strong>Output:</strong> &quot;0.(012)&quot;
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>-2<sup>31</sup> &lt;=&nbsp;numerator, denominator &lt;= 2<sup>31</sup> - 1</code></li>
	<li><code>denominator != 0</code></li>
</ul>
Hash Table; Math; String
function fractionToDecimal(numerator: number, denominator: number): string {
    if (numerator === 0) {
        return '0';
    }
    const sb: string[] = [];
    const neg: boolean = numerator > 0 !== denominator > 0;
    sb.push(neg ? '-' : '');
    let a: number = Math.abs(numerator),
        b: number = Math.abs(denominator);
    sb.push(Math.floor(a / b).toString());
    a %= b;
    if (a === 0) {
        return sb.join('');
    }
    sb.push('.');
    const d: Map<number, number> = new Map();
    while (a !== 0) {
        d.set(a, sb.length);
        a *= 10;
        sb.push(Math.floor(a / b).toString());
        a %= b;
        if (d.has(a)) {
            sb.splice(d.get(a)!, 0, '(');
            sb.push(')');
            break;
        }
    }
    return sb.join('');
}
