<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 UniFond{
    int* root;
    int* rank;
    public:
        UniFond(int size){
            root=new int[size];
            rank=new int[size];
            for(int i=0;i<size;i++){
                root[i]=i;
            }
        }
        int find(int node){
            if (node==root[node]) return node;
            int parent=find(root[node]);
            return parent;
        }
    void Union(int node_1, int node_2){
        int root_1=find(node_1);
        int root_2=find(node_2);
        if (root_1==root_2) return;
        
        if(rank[root_1]>rank[root_2]){
            root[root_2]=root_1;
            rank[root_1]++;
        }
        else{
            root[root_1]=root_2;
            rank[root_2]++;
        }
        return;
    }
    
};
class Solution {
public:
    string smallestStringWithSwaps(string s, vector<vector<int>>& pairs) {
        UniFond uni(s.size());
        for(int i=0;i<pairs.size();i++){
            uni.Union(pairs[i][0], pairs[i][1]);
        }
        unordered_map<int, vector<int>> Tree;//{root, {idx1, idx2}}
        
        for(int i=0;i<s.size();i++){
            int parent=uni.find(i);
            Tree[parent].push_back(i);
        }
        
        for(auto iter=Tree.begin();iter!=Tree.end();iter++){
            string tmp="";            
            for(int idx:iter->second){
                tmp+=s[idx];
            }
            sort(tmp.begin(),tmp.end());
            int i=0;
            for(int idx:iter->second){
                s[idx]=tmp[i++];
            }
        }
        return s;
        
        
        
        
        
        
        
    }
};
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