Maximum Length Substring With Two Occurrences
Given a string <code>s</code>, return the <strong>maximum</strong> length of a <span data-keyword="substring">substring</span>&nbsp;such that it contains <em>at most two occurrences</em> of each character.

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

<div class="example-block">
<p><strong>Input:</strong> <span class="example-io">s = &quot;bcbbbcba&quot;</span></p>

<p><strong>Output:</strong> <span class="example-io">4</span></p>

<p><strong>Explanation:</strong></p>
The following substring has a length of 4 and contains at most two occurrences of each character: <code>&quot;bcbb<u>bcba</u>&quot;</code>.</div>

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

<div class="example-block">
<p><strong>Input:</strong> <span class="example-io">s = &quot;aaaa&quot;</span></p>

<p><strong>Output:</strong> <span class="example-io">2</span></p>

<p><strong>Explanation:</strong></p>
The following substring has a length of 2 and contains at most two occurrences of each character: <code>&quot;<u>aa</u>aa&quot;</code>.</div>

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

<ul>
	<li><code>2 &lt;= s.length &lt;= 100</code></li>
	<li><code>s</code> consists only of lowercase English letters.</li>
</ul>
Hash Table; String; Sliding Window
class Solution:
    def maximumLengthSubstring(self, s: str) -> int:
        cnt = Counter()
        ans = i = 0
        for j, c in enumerate(s):
            cnt[c] += 1
            while cnt[c] > 2:
                cnt[s[i]] -= 1
                i += 1
            ans = max(ans, j - i + 1)
        return ans
