greatest-english-letter-in-upper-and-lower-case

java

python3

python

javascript

typescript

csharp

golang

kotlin

swift

rust

ruby

dart

scala

elixir

erlang

racket

bash

mysql

mssql

postgresql

oraclesql

pythondata

Algorithms

Given a string of English letters <code>s</code>, return the greatest English letter which occurs as both a lowercase and uppercase letter in <code>s</code>. The returned letter should be in uppercase. If no such letter exists, return an empty string.

An English letter <code>b</code> is greater than another letter <code>a</code> if <code>b</code> appears after <code>a</code> in the English alphabet.

&nbsp;
Example 1:

<pre>
Input: s = &quot;lEeTcOdE&quot;
Output: &quot;E&quot;
Explanation:
The letter &#39;E&#39; is the only letter to appear in both lower and upper case.
</pre>

Example 2:

<pre>
Input: s = &quot;arRAzFif&quot;
Output: &quot;R&quot;
Explanation:
The letter &#39;R&#39; is the greatest letter to appear in both lower and upper case.
Note that &#39;A&#39; and &#39;F&#39; also appear in both lower and upper case, but &#39;R&#39; is greater than &#39;F&#39; or &#39;A&#39;.
</pre>

Example 3:

<pre>
Input: s = &quot;AbCdEfGhIjK&quot;
Output: &quot;&quot;
Explanation:
There is no letter that appears in both lower and upper case.
</pre>

&nbsp;
Constraints:

<ul>
	<li><code>1 &lt;= s.length &lt;= 1000</code></li>
	<li><code>s</code> consists of lowercase and uppercase English letters.</li>
</ul>