<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> dfs(int u, vector<int>graph[], vector<bool>& visit) 
    {
        vector<int> cmb;
        stack<int> S;
        S.push(u);
        visit[u] = true;
        cmb.push_back(u);
        while(!S.empty()) 
        {
            int uu = S.top();
            S.pop();
            for(auto v: graph[uu]) 
            {
                if(visit[v] == false) 
                {
                    visit[v] = true;
                    S.push(v);
                    cmb.push_back(v);
                }
            }
        }
        return cmb;
     }    
    
    string smallestStringWithSwaps(string s, vector<vector<int>>& pairs) 
    {
        int n = s.size();
        vector<int> adj[n];
        for(auto it: pairs)
        {
            adj[it[0]].push_back(it[1]);
            adj[it[1]].push_back(it[0]);
        }

        vector<vector<int>> connected;
        vector<bool> vis(n,false);

        for(int i = 0;i<n;i++)
        {
            if(!vis[i])
            connected.push_back(dfs(i,adj,vis));
        }
        
        string ans = s;
        for(auto it: connected)
        {
            vector<int> charpos;
            vector<char> character;
            for(int i = 0;i<it.size();i++)
            {
                charpos.push_back(it[i]);
                character.push_back(s[it[i]]);
            }

            sort(charpos.begin(),charpos.end());
            sort(character.begin(),character.end());

            for(int i=0;i<it.size();i++)
                ans[charpos[i]] = character[i];
        }
        return ans;
    }
};
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