<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:
  vector<int>parent;
  vector<int>rank;
  int find(int u){
    if(parent[u]==u)return u;
    return parent[u]=find(parent[u]);
  }
  void dsu(int u,int v){
    int x=find(u);
    int y=find(v);
    if(x==y)return;
    if(rank[x]>rank[y]){
        parent[y]=x;
    }
    else if(parent[y]>parent[x]){
        parent[x]=y;
    }
    else {
        parent[y]=x;
        rank[x]++;
    }
  }
    string smallestStringWithSwaps(string s, vector<vector<int>>& pairs) {
        int n=s.size();
        parent.resize(n,0);
        for(int i=0;i<n;i++){
            parent[i]=i;
        }
        rank.resize(n,0);
        for(auto it:pairs){
            int u=it[0];
            int v=it[1];
            dsu(u,v);
        }
        unordered_map<int,set<int>>m;
        for(auto it:pairs){
            int x=find(it[0]);
            int v=find(it[1]);
            m[x].insert(it[0]);
            m[v].insert(it[1]);
        }
        for(auto it:m){
            vector<int>check;
            vector<char>let;
             for(auto &v:it.second){
               check.push_back(v);
               let.push_back(s[v]);
             }
             sort(check.begin(),check.end());
             sort(let.begin(),let.end());
             for(int i=0;i<check.size();i++){
                s[check[i]]=let[i];
             }
        }
        return s;
    }
};
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