<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 Solution {
    bool isSimilar(string &s1, string &s2) {
        char m1, m2, m3, m4;
        int mismatchs = 0;
        for (int i = 0; i < s1.length(); ++i) {
            if (s1[i] != s2[i]) {
                mismatchs++;
                if (mismatchs == 1) m1 = s1[i], m2 = s2[i];
                else m3 = s1[i], m4 = s2[i];
            }
        }

        if (mismatchs == 0) return true;
        if (mismatchs == 2 && m1 == m4 && m2 == m3) return true;
        return false;
    }
    void unn(int a, int b, int par[]) {
        int ra = getR(a, par), rb = getR(b, par);
        if (ra == rb) return;
        par[rb] = ra;
    }

    int getR(int x, int par[]) {
        if (par[x] == x) return x;
        return par[x] = getR(par[x], par);
    }
public:
    int numSimilarGroups(vector<string>& strs) {
        int n = strs.size();
        int par[n];
        for (int i = 0; i < n; ++i) par[i] = i;

        for (int i = 1; i < n; ++i) {
            for (int j = i-1; j >= 0; --j) {
                if (isSimilar(strs[i], strs[j])) {
                    unn(i, j, par);
                }
            }
        }

        int groups = 0;
        for (int i = 0; i < n; ++i) if (par[i] == i) ++groups;

        return groups;
    }
};
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