<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 {

private:
    int set_or_recur_parent(vector<int>& parent,int u){
        if(parent[u]==-1 || parent[u] == u ){
            return u;
        }
        return parent[u]=set_or_recur_parent(parent,parent[u]);
    }
public:
    string smallestStringWithSwaps(string s, vector<vector<int>>& pairs) {
        //build a data struct for union
        int size = s.size();
        vector<int> parent(size,-1);
        for(auto e: pairs){
            int v = e[0];
            int u = e[1];
            int v_p = set_or_recur_parent(parent,v);
            int u_p = set_or_recur_parent(parent,u);
            // int min_ = min(min(v_p,u_p),min(u,v));
            // parent[v] = min_;
            // parent[u] = min_;
            if(v_p!=u_p){
                parent[u_p]=v;
            }
        }
        map<int,vector<int>> char_sets;
        for(int i=0;i<size;i++){
            int group_id = set_or_recur_parent(parent,i);
            if(group_id!=-1){
                char_sets[group_id].emplace_back(i);
            }
        }
        for(auto& pair: char_sets){
            vector<int> char_index = pair.second;
            // vector<std::pair<char,int>> char_id_pair_list;
            vector<char> char_list;
            vector<int> id_list;
            for(int id: char_index){
                cout<<id<<" \n";
                char_list.emplace_back(s[id]);
                id_list.emplace_back(id);
            }
            auto cmp = [](std::pair<char,int> a, std::pair<char,int> b){
                return a.first>b.first;
            };
            // std::sort(char_id_pair_list.begin(),char_id_pair_list.end(),cmp);
            std::sort(char_list.begin(),char_list.end());
            std::sort(id_list.begin(),id_list.end());
            //update the original string
            for(int i=0;i<id_list.size();i++){
                s[id_list[i]] = char_list[i];
            }
        }
        return s;
    }
};
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