<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 dsu{
   public:
   vector<int>parent,size;
   dsu(int n){
    parent.resize(n);
    size.resize(n);
    for(int i=0;i<n;i++){
        parent[i]=i;
        size[i]=1;
    }
   }
   int find(int u){
    if(parent[u]==u)return u;
    return parent[u]=find(parent[u]);
   }
   void Union(int u,int v){
    int p=find(u);
    int q=find(v);
    if(p==q)return;
    if(size[p]<=size[q]){
        parent[p]=q;
        size[q]+=size[p];
    }
    else{
         parent[q]=p;
        size[p]+=size[q];
    }
   }
};


class Solution {
public:
    string smallestStringWithSwaps(string s, vector<vector<int>>& pairs) {
        for(auto i:pairs){
        int u=i[0],v=i[1];
        if(u>v)swap(u,v);
       }
        sort(pairs.begin(),pairs.end());

        int n=s.size();
       dsu ds(n);
       for(auto i:pairs){
        int u=i[0],v=i[1];
        ds.Union(u,v);
       }
       vector<vector<int>>v(n);
       for(int i=0;i<n;i++)v[ds.find(i)].push_back(i);
       
       for(int i=0;i<n;i++){
        if(v[i].size()==0)continue;
        sort(v[i].begin(),v[i].end());
        string r;
        for(int j=0;j<v[i].size();j++){
           r.push_back(s[v[i][j]]);
       }
       sort(r.begin(),r.end());
       for(int j=0;j<v[i].size();j++){
           s[v[i][j]]=r[j];
       }
       }
       return s;
    }
    
};
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