<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(vector<vector<int>> &g, vector<bool> &vis, vector<int> &index, string &str, int i, string &s) {
        vis[i] = true;
        str += s[i];
        index.push_back(i);

        for(int j=0;j<g[i].size();j++) {
            if(!vis[g[i][j]]) {
                dfs(g,vis,index,str,g[i][j],s);
            }
        }
    }

    string smallestStringWithSwaps(string s, vector<vector<int>>& pairs) {

        int l = s.length();
        vector<vector<int>> g(l);
        for(int i=0;i<pairs.size();i++) {
            g[pairs[i][0]].push_back(pairs[i][1]);
            g[pairs[i][1]].push_back(pairs[i][0]);
        }

        vector<bool> vis(l);
        for(int i=0;i<l;i++) {
            if(!vis[i]) {
                vector<int> index;
                string str = "";
                dfs(g, vis, index, str, i, s);
                sort(str.begin(), str.end());
                sort(index.begin(),index.end());
                for(int i=0;i<index.size();i++) {
                    s[index[i]] = str[i];
                }
            }
        }
        return s;
        
    }
};
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