Mean of Array After Removing Some Elements
<p>Given an integer array <code>arr</code>, return <em>the mean of the remaining integers after removing the smallest <code>5%</code> and the largest <code>5%</code> of the elements.</em></p>

<p>Answers within <code>10<sup>-5</sup></code> of the <strong>actual answer</strong> will be considered accepted.</p>

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

<pre>
<strong>Input:</strong> arr = [1,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,3]
<strong>Output:</strong> 2.00000
<strong>Explanation:</strong> After erasing the minimum and the maximum values of this array, all elements are equal to 2, so the mean is 2.
</pre>

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

<pre>
<strong>Input:</strong> arr = [6,2,7,5,1,2,0,3,10,2,5,0,5,5,0,8,7,6,8,0]
<strong>Output:</strong> 4.00000
</pre>

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

<pre>
<strong>Input:</strong> arr = [6,0,7,0,7,5,7,8,3,4,0,7,8,1,6,8,1,1,2,4,8,1,9,5,4,3,8,5,10,8,6,6,1,0,6,10,8,2,3,4]
<strong>Output:</strong> 4.77778
</pre>

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

<ul>
	<li><code>20 &lt;= arr.length &lt;= 1000</code></li>
	<li><code>arr.length</code><b> </b><strong>is a multiple</strong> of <code>20</code>.</li>
	<li><code><font face="monospace">0 &lt;= arr[i] &lt;= 10<sup>5</sup></font></code></li>
</ul>
Array; Sorting
function trimMean(arr: number[]): number {
    arr.sort((a, b) => a - b);
    let n = arr.length,
        rmLen = n * 0.05;
    let sum = 0;
    for (let i = rmLen; i < n - rmLen; i++) {
        sum += arr[i];
    }
    return sum / (n * 0.9);
}
