lexicographically-smallest-string-after-reverse

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Algorithms

You are given a string <code>s</code> of length <code>n</code> consisting of lowercase English letters.

You must perform exactly one operation by choosing any integer <code>k</code> such that <code>1 &lt;= k &lt;= n</code> and either:

<ul>
	<li>reverse the first <code>k</code> characters of <code>s</code>, or</li>
	<li>reverse the last <code>k</code> characters of <code>s</code>.</li>
</ul>

Return the lexicographically smallest string that can be obtained after exactly one such operation.

&nbsp;
Example 1:

<div class="example-block">
Input: s = &quot;dcab&quot;

Output: &quot;acdb&quot;

Explanation:

<ul>
	<li>Choose <code>k = 3</code>, reverse the first 3 characters.</li>
	<li>Reverse <code>&quot;dca&quot;</code> to <code>&quot;acd&quot;</code>, resulting string <code>s = &quot;acdb&quot;</code>, which is the lexicographically smallest string achievable.</li>
</ul>
</div>

Example 2:

<div class="example-block">
Input: s = &quot;abba&quot;

Output: &quot;aabb&quot;

Explanation:

<ul>
	<li>Choose <code>k = 3</code>, reverse the last 3 characters.</li>
	<li>Reverse <code>&quot;bba&quot;</code> to <code>&quot;abb&quot;</code>, so the resulting string is <code>&quot;aabb&quot;</code>, which is the lexicographically smallest string achievable.</li>
</ul>
</div>

Example 3:

<div class="example-block">
Input: s = &quot;zxy&quot;

Output: &quot;xzy&quot;

Explanation:

<ul>
	<li>Choose <code>k = 2</code>, reverse the first 2 characters.</li>
	<li>Reverse <code>&quot;zx&quot;</code> to <code>&quot;xz&quot;</code>, so the resulting string is <code>&quot;xzy&quot;</code>, which is the lexicographically smallest string achievable.</li>
</ul>
</div>

&nbsp;
Constraints:

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