<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 Disjoint{

    public :
    vector<int>parent;
    vector<int>size;

    Disjoint(int n){
        parent.resize(n+1);
        size.resize(n+1);
        for(int i=0;i<n+1;i++){
            parent[i]=i;
            size[i]=1;
        }
    }

    int find(int u){
        if(u==parent[u]) {
            return u;
        }
        return parent[u]=find(parent[u]);
    }

    void unite(int u,int v){
        int upar=find(u);
        int vpar=find(v);

        if(upar==vpar) return  ;
        if(size[upar] >=size[vpar]){
            parent[vpar]=upar;
            size[upar]+=size[vpar];
        }
        else{
            parent[upar]=vpar;
            size[vpar]+=size[upar];
        }
    }
};


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

        int n=s.length();
        Disjoint ds(n);

        for(auto it:pairs){
            ds.unite(it[0],it[1]);
        }
        
        unordered_map<int,vector<int>>mp;
        vector<int>com;
        for(int i=0;i<n;i++){
            int upar=ds.find(i);
            mp[upar].push_back(i);
        }
        unordered_map<int,string>mp2;
        for(auto it:mp){
            vector<int>vect=it.second;
            sort(it.second.begin(),it.second.end());
            string str="";
            for(auto ind:vect){
                str.push_back(s[ind]);
            }
            sort(str.begin(),str.end());
            mp2[it.first]=str;
        }
        for(auto it:mp){
            vector<int>vect=it.second;
            string str=mp2[it.first];
            int i=0;
            for(auto ind:vect){
                s[ind]=str[i];
                i++;
            }
        }
        return s;
    }
};
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