<p>You are given a string <code>s</code> and an integer <code>k</code>, a <code>k</code> <strong>duplicate removal</strong> consists of choosing <code>k</code> adjacent and equal letters from <code>s</code> and removing them, causing the left and the right side of the deleted substring to concatenate together.</p>

<p>We repeatedly make <code>k</code> <strong>duplicate removals</strong> on <code>s</code> until we no longer can.</p>

<p>Return <em>the final string after all such duplicate removals have been made</em>. It is guaranteed that the answer is <strong>unique</strong>.</p>

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

<pre>
<strong>Input:</strong> s = &quot;abcd&quot;, k = 2
<strong>Output:</strong> &quot;abcd&quot;
<strong>Explanation: </strong>There&#39;s nothing to delete.</pre>

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

<pre>
<strong>Input:</strong> s = &quot;deeedbbcccbdaa&quot;, k = 3
<strong>Output:</strong> &quot;aa&quot;
<strong>Explanation: 
</strong>First delete &quot;eee&quot; and &quot;ccc&quot;, get &quot;ddbbbdaa&quot;
Then delete &quot;bbb&quot;, get &quot;dddaa&quot;
Finally delete &quot;ddd&quot;, get &quot;aa&quot;</pre>

<p><strong class="example">Example 3:</strong></p>

<pre>
<strong>Input:</strong> s = &quot;pbbcggttciiippooaais&quot;, k = 2
<strong>Output:</strong> &quot;ps&quot;
</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>2 &lt;= k &lt;= 10<sup>4</sup></code></li>
	<li><code>s</code> only contains lowercase English letters.</li>
</ul>

class Solution:
    def removeDuplicates(self, s: str, k: int) -> str:
        counts = [(s[0],0)]
        for c in s:
            if c == counts[-1][0]:
                counts[-1] = (counts[-1][0], (counts[-1][1] + 1) % k)
            else:
                counts.append((c, 1))
           
        def compact():
            i = 1
            prev = 0
            while i < len(counts): 
                if counts[i] and counts[i][1]==0:
                    counts[i] = None
                if counts[i] == None:
                    i += 1
                    continue
                
                while prev > 0 and counts[prev] == None:
                    prev -= 1
                if prev >= 0 and counts[prev] and counts[i][0] == counts[prev][0]:
                    cnt =  (counts[i][1]+counts[prev][1]) % k
                    counts[i] = None if cnt == 0 else (counts[i][0], cnt)
                    counts[prev] = None
                prev = i if counts[i] else prev
                i += 1

        compact()

        res = []
        for v in counts:
            if v:
                res.append(v[0]*v[1])
        
        return "".join(res)
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