<h2><a href="https://leetcode.com/problems/minimum-deletions-to-make-string-balanced/">1653. Minimum Deletions to Make String Balanced</a></h2><h3>Medium</h3><hr><div><p>You are given a string <code>s</code> consisting only of characters <code>'a'</code> and <code>'b'</code>​​​​.</p>

<p>You can delete any number of characters in <code>s</code> to make <code>s</code> <strong>balanced</strong>. <code>s</code> is <strong>balanced</strong> if there is no pair of indices <code>(i,j)</code> such that <code>i &lt; j</code> and <code>s[i] = 'b'</code> and <code>s[j]= 'a'</code>.</p>

<p>Return <em>the <strong>minimum</strong> number of deletions needed to make </em><code>s</code><em> <strong>balanced</strong></em>.</p>

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

<pre><strong>Input:</strong> s = "aababbab"
<strong>Output:</strong> 2
<strong>Explanation:</strong> You can either:
Delete the characters at 0-indexed positions 2 and 6 ("aa<u>b</u>abb<u>a</u>b" -&gt; "aaabbb"), or
Delete the characters at 0-indexed positions 3 and 6 ("aab<u>a</u>bb<u>a</u>b" -&gt; "aabbbb").
</pre>

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

<pre><strong>Input:</strong> s = "bbaaaaabb"
<strong>Output:</strong> 2
<strong>Explanation:</strong> The only solution is to delete the first two characters.
</pre>

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

<ul>
	<li><code>1 &lt;= s.length &lt;= 10<sup>5</sup></code></li>
	<li><code>s[i]</code> is&nbsp;<code>'a'</code> or <code>'b'</code>​​.</li>
</ul>
</div>