<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 {
public:
    int longestAwesome(string s) {
        int n = s.size();
        int alphabetSize = 10;

        map<int, int> masks_indexes;
        masks_indexes[0] = -1;

        int mask = 0;
        int max_length = 0;

        for(int i = 0; i < n; i++){
            mask ^= 1 << (s[i] - '0');

            if(!masks_indexes.count(mask))
                masks_indexes[mask] = i;
            else
                max_length = max(max_length, 
                                i - masks_indexes[mask]);

            // If the is the same mask or mask different for 1 bit
            for(int j = 0; j < alphabetSize; j++) {
                int symbol = 1 << j;
                int newMask = mask ^ symbol;
                if(masks_indexes.count(newMask))
                    max_length = max(max_length, 
                                    i - masks_indexes[newMask]);
            }
        }
        return max_length;
    }
};
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