<p>You are given a string <code>s</code>, and an array of pairs of indices in the string&nbsp;<code>pairs</code>&nbsp;where&nbsp;<code>pairs[i] =&nbsp;[a, b]</code>&nbsp;indicates 2 indices(0-indexed) of the string.</p>

<p>You can&nbsp;swap the characters at any pair of indices in the given&nbsp;<code>pairs</code>&nbsp;<strong>any number of times</strong>.</p>

<p>Return the&nbsp;lexicographically smallest string that <code>s</code>&nbsp;can be changed to after using the swaps.</p>

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

<pre>
<strong>Input:</strong> s = &quot;dcab&quot;, pairs = [[0,3],[1,2]]
<strong>Output:</strong> &quot;bacd&quot;
<strong>Explaination:</strong> 
Swap s[0] and s[3], s = &quot;bcad&quot;
Swap s[1] and s[2], s = &quot;bacd&quot;
</pre>

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

<pre>
<strong>Input:</strong> s = &quot;dcab&quot;, pairs = [[0,3],[1,2],[0,2]]
<strong>Output:</strong> &quot;abcd&quot;
<strong>Explaination: </strong>
Swap s[0] and s[3], s = &quot;bcad&quot;
Swap s[0] and s[2], s = &quot;acbd&quot;
Swap s[1] and s[2], s = &quot;abcd&quot;</pre>

<p><strong class="example">Example 3:</strong></p>

<pre>
<strong>Input:</strong> s = &quot;cba&quot;, pairs = [[0,1],[1,2]]
<strong>Output:</strong> &quot;abc&quot;
<strong>Explaination: </strong>
Swap s[0] and s[1], s = &quot;bca&quot;
Swap s[1] and s[2], s = &quot;bac&quot;
Swap s[0] and s[1], s = &quot;abc&quot;
</pre>

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

<ul>
	<li><code>1 &lt;= s.length &lt;= 10^5</code></li>
	<li><code>0 &lt;= pairs.length &lt;= 10^5</code></li>
	<li><code>0 &lt;= pairs[i][0], pairs[i][1] &lt;&nbsp;s.length</code></li>
	<li><code>s</code>&nbsp;only contains lower case English letters.</li>
</ul>

class Solution {
public:
    int find(int a,vector<int>& parent)
    {
        if(parent[a]==a) return a;
        int ans=find(parent[a],parent);
        parent[a]=ans;
        return ans;
    }
    void combine(int a,int b,vector<int>& parent,vector<int>& rank,vector<vector<int>>& pos,vector<vector<char>>& chars)
    {
        int p1=find(a,parent),p2=find(b,parent);

        if(p1==p2) return;

        if(rank[p1]<rank[p2])
        {
            parent[p1]=p2;
            vector<int> dup1=pos[p1];
            vector<char> dup2=chars[p1];

            int len=dup1.size();

            for(int i=0;i<len;i++)
            {
                pos[p2].push_back(dup1[i]);
                chars[p2].push_back(dup2[i]);
            }
        }
        else if(rank[p2]<=rank[p1])
        {
            parent[p2]=p1;
            vector<int> dup1=pos[p2];
            vector<char> dup2=chars[p2];

            int len=dup1.size();

            for(int i=0;i<len;i++)
            {
                pos[p1].push_back(dup1[i]);
                chars[p1].push_back(dup2[i]);
            }

            if(rank[p2]==rank[p1]) rank[p1]++;
        }
    }

    string smallestStringWithSwaps(string s, vector<vector<int>>& pairs) {
        
        int n=s.length();
        
        vector<vector<int>> pos(n);
        vector<vector<char>> chars(n);
        vector<int> parent(n);
        vector<int> rank(n);

        for(int i=0;i<n;i++) rank[i]=1;

        iota(parent.begin(),parent.end(),0);
        for(int i=0;i<n;i++)
        {
            pos[i].push_back(i);
            chars[i].push_back(s[i]);
        }

        for(auto a:pairs) 
        {
            combine(a[0],a[1],parent,rank,pos,chars);
        }

        for(int i=0;i<n;i++)
        {
            if(parent[i]==i)
            {
                sort(pos[i].begin(),pos[i].end());
                sort(chars[i].begin(),chars[i].end());
                int len=pos[i].size();

                for(int j=0;j<len;j++) s[pos[i][j]]=chars[i][j];
            }
        }
        return s;
    }
};
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