<p>You are given a string <code>s</code> consisting only of characters <code>&#39;a&#39;</code> and <code>&#39;b&#39;</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] = &#39;b&#39;</code> and <code>s[j]= &#39;a&#39;</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 = &quot;aababbab&quot;
<strong>Output:</strong> 2
<strong>Explanation:</strong> You can either:
Delete the characters at 0-indexed positions 2 and 6 (&quot;aa<u>b</u>abb<u>a</u>b&quot; -&gt; &quot;aaabbb&quot;), or
Delete the characters at 0-indexed positions 3 and 6 (&quot;aab<u>a</u>bb<u>a</u>b&quot; -&gt; &quot;aabbbb&quot;).
</pre>

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

<pre>
<strong>Input:</strong> s = &quot;bbaaaaabb&quot;
<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>&#39;a&#39;</code> or <code>&#39;b&#39;</code>​​.</li>
</ul>

class Solution:
    def minimumDeletions(self, s: str) -> int:
    
        if len(s) == 0:
            return 0
        n = len(s) 
        dela = [0 for i in range(n+1)]
        delb = [0 for i in range(n+1)]  
        bdel = 0
        adel = 0 
        k = s.index("b") if "b" in s else -1
        l = n-1-s[::-1].index("a") if "a" in s else -1 
        if k == -1 or l == -1:
            return 0
        #print(k,l)
        for i in range(n):
            if s[i]  == "b":
                bdel += 1
            delb[i] = bdel
            j = n -1 -i 
            if s[j] == "a":
                adel += 1
            dela[j]  = adel
        # print(delb)
        # print(dela)

        total = n
        for i in range(k,l):
            
            #val = delb[i]+dela[i+1]
            total = min(total,delb[i]+dela[i+1])
        total = min(total, dela[k], delb[l])    
        return total      


            
        
22351