<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 {
    void dfs(unordered_map<int,vector<int>>& graph,string& s,set<int>& idxs,vector<char>& chars,vector<bool>& visited, int idx){
        idxs.insert(idx);
        chars.push_back(s[idx]);

        for(int& next:graph[idx]){
            if(!visited[next]){
                visited[next]=true;
                dfs(graph,s,idxs,chars,visited,next);
            }
        }
    }  
    void bucketSort(vector<char>& chars){
        int arr[26]={0};
        for(char& ch:chars) arr[ch-'a']++;
        for(int i=0,j=0;i<26;i++){
            while(arr[i]>0){
                chars[j++]=(char)i+97;
                arr[i]--;
            }
        }
    }
    void placeCharsInString(string& s, set<int>& idxs, vector<char>& chars){
        bucketSort(chars);
        int i=0;
        for(set<int>::iterator itr=idxs.begin();itr!=idxs.end();itr++){
            s[*itr]=chars[i++];
        }
    }
public:
    string smallestStringWithSwaps(string& s, vector<vector<int>>& pairs) {
        unordered_map<int,vector<int>> graph;
        for(vector<int>& pair:pairs){
            graph[pair[0]].push_back(pair[1]);
            graph[pair[1]].push_back(pair[0]);
        }
        vector<bool> visited(s.size(),false);
        for(int i=0;i<s.size();i++){
            if(!visited[i]){
                visited[i]=true;
                set<int> idxs;
                vector<char> chars;
                dfs(graph,s,idxs,chars,visited,i);
                placeCharsInString(s,idxs,chars);
            }
        }
        return s;
    }
};
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