<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> indices;                                                 //Stores indices of same group.
    vector<bool> visited;
    vector<vector<int>> adjList;
    string indiceString;                                                 //Stores  string formed by indices in the same group.
    void dfs(string &s,int n)                                             //DFS to get all indices in same group.
    {
        visited[n]=true;
        indices.push_back(n);
        indiceString+=s[n];
        for(int &i:adjList[n])
            if(!visited[i])
               dfs(s,i);
    }
    string smallestStringWithSwaps(string s, vector<vector<int>>& pairs) 
    {
        adjList.resize(s.length());
        visited.resize(s.length(),false);
        for(vector<int> &v:pairs)                               //Create adjacency list using the indice pairs
            adjList[v[0]].push_back(v[1]),adjList[v[1]].push_back(v[0]);
        for(int i=0;i<s.length();i++)
            if(!visited[i])
            {
                indiceString="";                              //Clear string formed by one group of indices before finding next group.
                indices.clear();                             //Clear indices vector before finding another group.
                dfs(s,i);
                sort(indiceString.begin(),indiceString.end());                    //Sort the characters in the same group.
                sort(indices.begin(),indices.end());                                  //Sort the indices in the same group.            
                for(int i=0;i<indices.size();i++)          //Replace all the indices in the same group with the sorted characters.
                    s[indices[i]]=indiceString[i];
            }
        return s;
    }
};
69987