<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 {
private:
    void dfs(string s, unordered_map<string,vector<string>>& mp, set<string>& visit){
        if (visit.count(s)) return;
        visit.insert(s);
        for (const auto neighbor:mp[s]){
            dfs(neighbor, mp, visit);
        }
    }
public:
    int numSimilarGroups(vector<string>& strs) {
        unordered_map<string,vector<string>> mp;
        int n = strs.size();
        int length = strs[0].size();
        for (int i=0;i<n;++i){
            for (int j=1;j<n;++j){
                int dif = 0;
                int count = 0;
                for (int k=0;k<length;++k){
                    if (strs[i][k] != strs[j][k]){
                        dif++;
                        count += strs[i][k] - strs[j][k];
                    }
                }
                if (count == 0 && (dif == 0 || dif == 2)){
                    mp[strs[i]].push_back(strs[j]);
                    mp[strs[j]].push_back(strs[i]);
                }
            }
        }
        set<string> visit;
        int ans = 0;
        for (const string& s:strs){
            if (!visit.count(s)){
                dfs(s,mp,visit);
                ans++;
            }
        }
        return ans;
    }
};
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