<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 {
    void dfs(vector<vector<int>>& adj, int i, set<int>& us) {
      //  cout<<i<<" ";
        if (us.find(i) != us.end())return ;
          cout<<i<<" ";
        us.insert(i);
        for(auto it : adj[i]) 
        dfs(adj, it, us);
    }
public:
    string smallestStringWithSwaps(string s, vector<vector<int>>& pairs) {
        int n = s.length();
        vector<vector<int>> adj(n);
        for(int i=0;i<pairs.size();i++) {
           adj[pairs[i][0]].push_back(pairs[i][1]);
           adj[pairs[i][1]].push_back(pairs[i][0]);
      }
    //  cout<<adj[0][0]<<" ";
      vector<bool> visited(n,0);
      for(int i=0;i<n;i++) {
        if (!visited[i]) {
           set<int> us;
          dfs(adj,  i, us);
            vector<char> x;
          for(auto it : us) {
        visited[it] = true;
          x.push_back(s[it]);
          }
          sort(x.begin(), x.end());
          int j=0;
          for(auto it: us) {
            //cout<<it<<" ";
            s[it] = x[j];
            j++;
          }
          
        }
      }
     return s;
    }
};
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