<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:
    void dfs(int i,vector <int> &vis,string &s,vector <vector <int>> &adj,vector <int> &indexes, vector <char> &chars){
        vis[i]=true;
        chars.push_back(s[i]);
        indexes.push_back(i);
        for(auto &val:adj[i]){
            if(!vis[val]) dfs(val,vis,s,adj,indexes,chars);
        }
    }
    string smallestStringWithSwaps(string s, vector<vector<int>>& pairs) {
        //solution 2 - DFS
        vector <vector <int>> adj(s.size());
        for(auto &pair:pairs){
            adj[pair[0]].push_back(pair[1]);
            adj[pair[1]].push_back(pair[0]);
        }
        vector <int> vis(s.size());
        for(int i=0;i<s.size();i++){
            if(!vis[i]){
                vector <int> indexes;
                vector <char> chars;
                dfs(i,vis,s,adj,indexes, chars);
                //dfs complete, operate here only
                sort(indexes.rbegin(),indexes.rend());
                sort(chars.rbegin(),chars.rend());
                while(indexes.size()){
                    s[indexes[indexes.size()-1]]=chars[indexes.size()-1];
                    chars.pop_back();
                    indexes.pop_back();
                }
            }
        }
        return s;
    }
};
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