<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 {
    class DSU{
    public:
        vector<int> parents;
        vector<int> nodeSize;
        DSU(int n){
            for(int i=0;i<n;i++) parents.push_back(i);
            nodeSize.resize(n,1);
        }
        int findParent(int node){
            if(parents[node]==node) return node;
            int par = findParent(parents[node]);
            parents[node]=par;
            return par;
        }
        void unionBySize(int x,int y){
            int parX = findParent(x);
            int parY = findParent(y);
            if(parX==parY) return;
            if(nodeSize[parX]>=nodeSize[parY]){
                parents[parY]=parX;
                nodeSize[parX]+=nodeSize[parY];
            }else{
                parents[parX]=parY;
                nodeSize[parY]+=nodeSize[parX];
            }
        }
    };
public:
    string smallestStringWithSwaps(string s, vector<vector<int>>& pairs) {
        DSU jai(s.size());
        for(auto& p:pairs){
            jai.unionBySize(p[0],p[1]);
        }
        unordered_map<int,vector<int>> mp;
        for(int i=0;i<s.size();i++){
            int par = jai.findParent(i);
            mp[par].push_back(i);
        }
        for(auto &p:mp){
            vector<int> idx = p.second;
            sort(idx.begin(),idx.end());
            string curr="";
            for(int i:idx) curr+=s[i];
            sort(curr.begin(),curr.end());
            for(int i=0;i<idx.size();i++) s[idx[i]]=curr[i];
        }
        return s;
    }
};
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