<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:
    bool flag[100011];

    vector<int> vec[100001], pos;

    vector<char> allChars;

    string str;
    string smallestStringWithSwaps(string s, vector<vector<int>>& pairs) {
       int n = pairs.size();

        for(int i=0;i<n;i++)flag[i] = false;

        str = s;

        for(int i=0;i<n;i++){

            int u = pairs[i][0];

            int v = pairs[i][1];

            

            vec[u].push_back(v);

            vec[v].push_back(u);

        }

        

        for(int i=0;i<n;i++){

            if(!flag[i]){

                pos.clear();

                allChars.clear();

                dfs(i);

                

                sort(allChars.begin(), allChars.end());

                sort(pos.begin(), pos.end());

                

                for(int j=0;j<pos.size();j++){

                    str[ pos[j] ] = allChars[j];

                }

            }

        }

        

        return str;

    }

    

    void dfs(int nd){

        flag[nd] = true;

        allChars.push_back(str[nd]);

        pos.push_back(nd);

        

        for(auto v: vec[nd]){

            if(!flag[v]){

                dfs(v);

            }

        } 
    }
};
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