<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 UnionFind {
    int size_;
    vector<int> father;
public:
    UnionFind(int size): size_(size), father(size) {
        for (int i = 0; i < size; i ++) {
            father[i] = i;
        }
    }

    int Find(int index) {
        if (father[index] != index) {
            father[index] = Find(father[index]);
        }
        return father[index];
    }

    void Union(int x, int y) {
        int fx = Find(x);
        int fy = Find(y);
        if (fx == fy)
            return;
        father[fx] = fy;
        size_--;
    }

    int Size() {
        return size_;
    }
};

class Solution {

    bool is_similar(string str1, string str2) {
        if (str1.size() != str2.size()) {
            return false;
        }
        int different_count = 0;

        char str1_different[3], str2_different[3];
        for (int i = 0; i < str1.size(); i ++) {
            if (str1[i] != str2[i]) {

                str1_different[different_count] = str1[i];
                str2_different[different_count] = str2[i];
                different_count ++;
            }
            if (different_count > 2) {
                return false;
            }
        }

        if (different_count == 0) {
            return true;
        } else if (different_count == 1) {
            return str1_different[0] == str2_different[0];
        } else if (different_count == 2) {
            return (str1_different[0] == str2_different[0] && str1_different[1] == str2_different[1]) ||
                    (str1_different[0] == str2_different[1] && str1_different[1] == str2_different[0]);
        }
        return false;
    }

public:
    int numSimilarGroups(vector<string>& strs) {
        UnionFind union_find(strs.size());
        for (int i = 0; i < strs.size(); i ++) {
            for (int j = i+1; j < strs.size(); j++) {
                if (is_similar(strs[i], strs[j])) {
                    union_find.Union(i, j);
                }
            }
        }
        return union_find.Size();
    }
};
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