<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 findUPar(int node,vector<int> &parent)
    {
        if(parent[node]==node)return node;
        return parent[node]=findUPar(parent[node],parent);
    }
    void unionBySize(vector<int> &size,int node1,int node2,vector<int> &parent)
    {
        int ulPar1=findUPar(node1,parent);
        int ulPar2=findUPar(node2,parent);
        if(ulPar1==ulPar2)return;
        if(size[ulPar1]>size[ulPar2])
        {
            parent[ulPar2]=ulPar1;
            size[ulPar1]+=size[ulPar2];
        }
        else
        {
            parent[ulPar1]=ulPar2;
            size[ulPar2]+=size[ulPar1];
        }
    }
    string smallestStringWithSwaps(string s, vector<vector<int>>& pairs) {
        int n=s.size();
        vector<int> vis(n,0);
        vector<int> size(n,1);
        vector<int> parent(n,0);
        for(int i=0;i<n;i++)parent[i]=i;
        unordered_map<int,vector<int>> mp;
        for(int i=0;i<pairs.size();i++)
        {
            int node1=pairs[i][0];
            int node2=pairs[i][1];
            unionBySize(size,node1,node2,parent);
        }
        for(int i=0;i<n;i++)
        {
            int ulPar=findUPar(i,parent);
            if(size[ulPar]>1)
            {
                mp[ulPar].push_back(i);
            }
        }
        for(auto &m:mp)
        {
            vector<int> indices=m.second;
            string temp;
            for(auto &idx:indices)
            {
                temp+=s[idx];
            }
            sort(temp.begin(),temp.end());
            int j=0;
            for(auto &idx:indices)
            {
                s[idx]=temp[j];
                j++;
            }
        }
        return s;
        
    }
};
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