<h2><a href="https://leetcode.com/problems/permutation-in-string/">567. Permutation in String</a></h2><h3>Medium</h3><hr><div><p>Given two strings <code>s1</code> and <code>s2</code>, return <code>true</code><em> if </em><code>s2</code><em> contains a permutation of </em><code>s1</code><em>, or </em><code>false</code><em> otherwise</em>.</p>

<p>In other words, return <code>true</code> if one of <code>s1</code>'s permutations is the substring of <code>s2</code>.</p>

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

<pre><strong>Input:</strong> s1 = "ab", s2 = "eidbaooo"
<strong>Output:</strong> true
<strong>Explanation:</strong> s2 contains one permutation of s1 ("ba").
</pre>

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

<pre><strong>Input:</strong> s1 = "ab", s2 = "eidboaoo"
<strong>Output:</strong> false
</pre>

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

<ul>
	<li><code>1 &lt;= s1.length, s2.length &lt;= 10<sup>4</sup></code></li>
	<li><code>s1</code> and <code>s2</code> consist of lowercase English letters.</li>
</ul>
</div>