<p>Design an algorithm to find the smallest K numbers in an array.</p>

<p><strong>Example: </strong></p>

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

<p><strong>Note: </strong></p>

<ul>
	<li><code>0 &lt;= len(arr) &lt;= 100000</code></li>
	<li><code>0 &lt;= k &lt;= min(100000, len(arr))</code></li>
</ul>