<p>You are given an array of strings of the same length <code>words</code>.</p>

<p>In one <strong>move</strong>, you can swap any two even indexed characters or any two odd indexed characters of a string <code>words[i]</code>.</p>

<p>Two strings <code>words[i]</code> and <code>words[j]</code> are <strong>special-equivalent</strong> if after any number of moves, <code>words[i] == words[j]</code>.</p>

<ul>
	<li>For example, <code>words[i] = &quot;zzxy&quot;</code> and <code>words[j] = &quot;xyzz&quot;</code> are <strong>special-equivalent</strong> because we may make the moves <code>&quot;zzxy&quot; -&gt; &quot;xzzy&quot; -&gt; &quot;xyzz&quot;</code>.</li>
</ul>

<p>A <strong>group of special-equivalent strings</strong> from <code>words</code> is a non-empty subset of words such that:</p>

<ul>
	<li>Every pair of strings in the group are special equivalent, and</li>
	<li>The group is the largest size possible (i.e., there is not a string <code>words[i]</code> not in the group such that <code>words[i]</code> is special-equivalent to every string in the group).</li>
</ul>

<p>Return <em>the number of <strong>groups of special-equivalent strings</strong> from </em><code>words</code>.</p>

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

<pre>
<strong>Input:</strong> words = [&quot;abcd&quot;,&quot;cdab&quot;,&quot;cbad&quot;,&quot;xyzz&quot;,&quot;zzxy&quot;,&quot;zzyx&quot;]
<strong>Output:</strong> 3
<strong>Explanation:</strong> 
One group is [&quot;abcd&quot;, &quot;cdab&quot;, &quot;cbad&quot;], since they are all pairwise special equivalent, and none of the other strings is all pairwise special equivalent to these.
The other two groups are [&quot;xyzz&quot;, &quot;zzxy&quot;] and [&quot;zzyx&quot;].
Note that in particular, &quot;zzxy&quot; is not special equivalent to &quot;zzyx&quot;.
</pre>

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

<pre>
<strong>Input:</strong> words = [&quot;abc&quot;,&quot;acb&quot;,&quot;bac&quot;,&quot;bca&quot;,&quot;cab&quot;,&quot;cba&quot;]
<strong>Output:</strong> 3
</pre>

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

<ul>
	<li><code>1 &lt;= words.length &lt;= 1000</code></li>
	<li><code>1 &lt;= words[i].length &lt;= 20</code></li>
	<li><code>words[i]</code> consist of lowercase English letters.</li>
	<li>All the strings are of the same length.</li>
</ul>

class Solution {
public:
    int numSpecialEquivGroups(vector<string>& words) {
        unordered_set<vector<vector<int>>, VectorHash> set;
        const int n = words[0].length();
        for(string& s: words){
            vector<vector<int>> v;
            vector<int> v1(26,0);
            for(int i{0}; i < n; i+=2) v1[ s[i]-'a']++;
            v.push_back(move(v1));
            vector<int> v2(26,0);
            for(int i{1}; i < n; i+=2) v2[ s[i]-'a']++;
            v.push_back(move(v2));
            set.insert(move(v));
        }       
        return set.size();
    }
struct VectorHash {
    size_t operator()(const std::vector<vector<int>>& v) const {
        std::hash<int> hasher;
        size_t seed = 0;
        for(int i{0}; i < v.size(); i++)
        for (int j{0}; j < v[i].size(); j++) {
            seed ^= hasher(v[i][j]) + 0x9e3779b9 + (seed<<6) + (seed>>2);
            }
        return seed;
    }
};
};
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