Decrypt String from Alphabet to Integer Mapping
<p>You are given a string <code>s</code> formed by digits and <code>&#39;#&#39;</code>. We want to map <code>s</code> to English lowercase characters as follows:</p>

<ul>
	<li>Characters (<code>&#39;a&#39;</code> to <code>&#39;i&#39;</code>) are represented by (<code>&#39;1&#39;</code> to <code>&#39;9&#39;</code>) respectively.</li>
	<li>Characters (<code>&#39;j&#39;</code> to <code>&#39;z&#39;</code>) are represented by (<code>&#39;10#&#39;</code> to <code>&#39;26#&#39;</code>) respectively.</li>
</ul>

<p>Return <em>the string formed after mapping</em>.</p>

<p>The test cases are generated so that a unique mapping will always exist.</p>

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

<pre>
<strong>Input:</strong> s = &quot;10#11#12&quot;
<strong>Output:</strong> &quot;jkab&quot;
<strong>Explanation:</strong> &quot;j&quot; -&gt; &quot;10#&quot; , &quot;k&quot; -&gt; &quot;11#&quot; , &quot;a&quot; -&gt; &quot;1&quot; , &quot;b&quot; -&gt; &quot;2&quot;.
</pre>

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

<pre>
<strong>Input:</strong> s = &quot;1326#&quot;
<strong>Output:</strong> &quot;acz&quot;
</pre>

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

<ul>
	<li><code>1 &lt;= s.length &lt;= 1000</code></li>
	<li><code>s</code> consists of digits and the <code>&#39;#&#39;</code> letter.</li>
	<li><code>s</code> will be a valid string such that mapping is always possible.</li>
</ul>
String
function freqAlphabets(s: string): string {
    const ans: string[] = [];
    for (let i = 0, n = s.length; i < n; ) {
        if (i + 2 < n && s[i + 2] === '#') {
            ans.push(String.fromCharCode(96 + +s.slice(i, i + 2)));
            i += 3;
        } else {
            ans.push(String.fromCharCode(96 + +s[i]));
            i++;
        }
    }
    return ans.join('');
}
