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Algorithms

Given an array of strings <code>words</code>, return the words that can be typed using letters of the alphabet on only one row of American keyboard like the image below.

Note that the strings are case-insensitive, both lowercased and uppercased of the same letter are treated as if they are at the same row.

In the American keyboard:

<ul>
	<li>the first row consists of the characters <code>&quot;qwertyuiop&quot;</code>,</li>
	<li>the second row consists of the characters <code>&quot;asdfghjkl&quot;</code>, and</li>
	<li>the third row consists of the characters <code>&quot;zxcvbnm&quot;</code>.</li>
</ul>
<img alt="" src="https://assets.leetcode.com/uploads/2018/10/12/keyboard.png" style="width: 800px; max-width: 600px; height: 267px;" />
&nbsp;
Example 1:

<div class="example-block">
Input: words = [&quot;Hello&quot;,&quot;Alaska&quot;,&quot;Dad&quot;,&quot;Peace&quot;]

Output: [&quot;Alaska&quot;,&quot;Dad&quot;]

Explanation:

Both <code>&quot;a&quot;</code> and <code>&quot;A&quot;</code> are in the 2nd row of the American keyboard due to case insensitivity.
</div>

Example 2:

<div class="example-block">
Input: words = [&quot;omk&quot;]

Output: []
</div>

Example 3:

<div class="example-block">
Input: words = [&quot;adsdf&quot;,&quot;sfd&quot;]

Output: [&quot;adsdf&quot;,&quot;sfd&quot;]
</div>

&nbsp;
Constraints:

<ul>
	<li><code>1 &lt;= words.length &lt;= 20</code></li>
	<li><code>1 &lt;= words[i].length &lt;= 100</code></li>
	<li><code>words[i]</code> consists of English letters (both lowercase and uppercase).&nbsp;</li>
</ul>