<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 DSU{
    public:
    #define vi vector<int>
    vi par,size;
    DSU(int n){
        par.resize(n+1);
        size.resize(n+1,1);
        for(int i=0;i<=n;i++)par[i]=i;
    }
    int f_up(int u){
        if(par[u]==u)return par[u];
        return par[u]=f_up(par[u]);
    }
    void ubs(int u,int v){
        int pu=f_up(u),pv=f_up(v);
        if(pu==pv)return;
        if(size[pu]>size[pv]){
            size[pu]+=size[pv];
            par[pv]=pu;
        }else{
            size[pv]+=size[pu];
            par[pu]=pv;
        }
    }
};
class Solution {
public:
    #define vi vector<int>
    #define vvi vector<vi>
    #define vc vector<char>
    #define pb push_back
    #define ff first
    #define ss second
    string smallestStringWithSwaps(string s, vvi &v) {
        int n=s.size();
        DSU ds(n);
        for(auto i:v){
            ds.ubs(i[0],i[1]);
        }
        map<int,vi>idx_mp;
        map<int,string>str_mp;
        for(int i=0;i<n;i++){
            int fp=ds.f_up(i);
            idx_mp[fp].pb(i);
            str_mp[fp]+=s[i];
        }
        for(auto &i:str_mp){
            sort(i.ss.begin(),i.ss.end());
        }
        vc ans(n);
        for(auto i:idx_mp){
            int j=i.ff;   
            vi idx=i.ss;
            for(int k=0;k<idx.size();k++)ans[idx[k]]=str_mp[j][k];
        }
        string p;
        for(auto i:ans)p+=i;
        return p;
    }
};
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