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

        int n = s.size();
        vector<vector<int>> graph(n);

        for (auto v : pairs){ // constructed a graph

            graph[v[0]].push_back(v[1]);
            graph[v[1]].push_back(v[0]);
        }

        vector<vector<int>> indices;
        vector<string> values;
        vector<bool> visited(n,false);

        for (int i=0; i<n; i++){
            if (!visited[i]){
                vector<int> temp;
                string res;
                dfs(graph,i,visited,temp,res,s);
                indices.push_back(temp);
                values.push_back(res);
            }
        }

        int v_size = indices.size();

        for (int i=0;i<v_size; i++){
            
            sort(indices[i].begin(),indices[i].end());
            sort(values[i].begin(),values[i].end());

            int s_size = values[i].size();

            for (int j=0; j<s_size; j++){
                s[indices[i][j]] = values[i][j];
            }
        }

        return s;
    }
//dfs(graph,i,visited,temp,res,s);
    void dfs(vector<vector<int>> &graph, int i, vector<bool> &visited, vector<int>& temp, string& res, string &s){

        visited[i] = true;
        temp.push_back(i);
        res += s[i];

        for (int val : graph[i]){
            if (!visited[val]){

                dfs(graph,val, visited, temp,res,s);
            }
        }
    }
};
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