<p>You are given a string <code>s</code>. An <strong>awesome</strong> substring is a non-empty substring of <code>s</code> such that we can make any number of swaps in order to make it a palindrome.</p>

<p>Return <em>the length of the maximum length <strong>awesome substring</strong> of</em> <code>s</code>.</p>

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

<pre>
<strong>Input:</strong> s = &quot;3242415&quot;
<strong>Output:</strong> 5
<strong>Explanation:</strong> &quot;24241&quot; is the longest awesome substring, we can form the palindrome &quot;24142&quot; with some swaps.
</pre>

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

<pre>
<strong>Input:</strong> s = &quot;12345678&quot;
<strong>Output:</strong> 1
</pre>

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

<pre>
<strong>Input:</strong> s = &quot;213123&quot;
<strong>Output:</strong> 6
<strong>Explanation:</strong> &quot;213123&quot; is the longest awesome substring, we can form the palindrome &quot;231132&quot; with some swaps.
</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</code> consists only of digits.</li>
</ul>

class Solution:
    def longestAwesome(self, s: str) -> int:
        pos={}
        mask = 0
        maxlen = 0
        pos[0] = -1 # Empty Prefix has mask 0 at index -1
        for i ,c in enumerate(s):
            digit = int(c)

            #Flip the bit corresponding to the current digit
            mask ^=(1<<digit)
            
            # Case 1: If current mask has seen before
            if mask in pos:
                maxlen = max(maxlen,i-pos[mask])
            else:
                pos[mask] = i # Record the earliest occurence of this mask
            
            # Case 2: Check mask that differ by one bit only

            for d in range(10):
                temp_mask = mask ^(1<<d)
                if temp_mask in pos :
                    maxlen = max(maxlen,i-pos[temp_mask])
        return maxlen
17300