<p>Two strings, <code>X</code> and <code>Y</code>, are considered similar if either they are identical or we can make them equivalent by swapping at most two letters (in distinct positions) within the string <code>X</code>.</p>

<p>For example, <code>&quot;tars&quot;</code>&nbsp;and <code>&quot;rats&quot;</code>&nbsp;are similar (swapping at positions <code>0</code> and <code>2</code>), and <code>&quot;rats&quot;</code> and <code>&quot;arts&quot;</code> are similar, but <code>&quot;star&quot;</code> is not similar to <code>&quot;tars&quot;</code>, <code>&quot;rats&quot;</code>, or <code>&quot;arts&quot;</code>.</p>

<p>Together, these form two connected groups by similarity: <code>{&quot;tars&quot;, &quot;rats&quot;, &quot;arts&quot;}</code> and <code>{&quot;star&quot;}</code>.&nbsp; Notice that <code>&quot;tars&quot;</code> and <code>&quot;arts&quot;</code> are in the same group even though they are not similar.&nbsp; Formally, each group is such that a word is in the group if and only if it is similar to at least one other word in the group.</p>

<p>We are given a list <code>strs</code> of strings where every string in <code>strs</code> is an anagram of every other string in <code>strs</code>. How many groups are there?</p>

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

<pre>
<strong>Input:</strong> strs = [&quot;tars&quot;,&quot;rats&quot;,&quot;arts&quot;,&quot;star&quot;]
<strong>Output:</strong> 2
</pre>

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

<pre>
<strong>Input:</strong> strs = [&quot;omv&quot;,&quot;ovm&quot;]
<strong>Output:</strong> 1
</pre>

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

<ul>
	<li><code>1 &lt;= strs.length &lt;= 300</code></li>
	<li><code>1 &lt;= strs[i].length &lt;= 300</code></li>
	<li><code>strs[i]</code> consists of lowercase letters only.</li>
	<li>All words in <code>strs</code> have the same length and are anagrams of each other.</li>
</ul>

class DSU {
public:
    vector<int> parent;
    vector<int> sizes;
    int components;
    DSU(int n) {
        parent.resize(n);
        iota(parent.begin(), parent.end(), 0);
        sizes.assign(n, 1);
        components = n;
    }
    int find(int u) {
        return u == parent[u] ? u : parent[u] = find(parent[u]);
    }
    bool unite(int u, int v) {
        u = find(u);
        v = find(v);
        if(u == v) {
            return false;
        }
        if(sizes[u] < sizes[v]) {
            swap(u, v);
        }
        parent[v] = u;
        sizes[u] += sizes[v];
        components--;
        return true;
    }
};
class Solution {
public:
    int numSimilarGroups(vector<string>& strs) {
        int n = strs.size();
        auto check = [&](int i, int j) {
            string s = strs[i];
            string t = strs[j];
            int cnt = 0;
            for(int i = 0; i < s.size(); i++) {
                cnt += s[i] != t[i];
            }
            return cnt <= 2;
        };
        DSU dsu(n);
        for(int i = 0; i < n; i++) {
            for(int j = 0; j < n; j++) {
                if(check(i, j)) {
                    dsu.unite(i, j);
                }
            }
        }
        return dsu.components;
    }
};
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