<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: 
    vector<int> parent,size;
    DSU(int n){
        parent.resize(n,0);
        size.resize(n,1);
        for(int i=0;i<n;i++){
            parent[i]=i;
        }
    }
    int fup(int node){
        if(node==parent[node]){
            return node;
        }
        return parent[node]=fup(parent[node]);
    }
    void ubs(int u,int v){
        int ulu=fup(u),ulv=fup(v);
        if(ulu==ulv){
            return;
        }
        if(size[ulv]>size[ulu]){
            swap(ulu,ulv);
        }
        size[ulu]+=size[ulv];
        parent[ulv]=ulu;
    }
};
class Solution {
public:
    string smallestStringWithSwaps(string s, vector<vector<int>>& pairs) {
        int n=s.size();
        DSU ds(n);
        for(auto it: pairs){
            int u=it[0],v=it[1];
            ds.ubs(u,v);
        }
        map<int,multiset<char>> m;
        for(int i=0;i<n;i++){
            m[ds.fup(i)].insert(s[i]);
        }
        string ans;
        for(int i=0;i<n;i++){
            int u=ds.fup(i);
            auto t=m[u].begin();
            ans.push_back(*t);
            m[u].erase(t);
        }
        return ans;
    }
};
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