<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 DisjointSet
{
public:
    vector<int> parent, size;
    DisjointSet(int n)
    {
        parent.resize(n+1);
        size.resize(n+1);
        for(int i=0; i<=n; i++) parent[i]=i;
    }
    int findParent(int u)
    {
        if(parent[u]==u) return u;
        return parent[u]=findParent(parent[u]);
    }
    void unionBySize(int u, int v)
    {
        int upu = findParent(u);
        int upv = findParent(v);
        int su = size[upu], sv = size[upv];
        if(su < sv)
        {
            parent[upu] = upv;
            size[upv] += size[upu];
        }
        else
        {
            parent[upv] = upu;
            size[upu] += size[upv];
        }
    }
};
class Solution {
public:
    string smallestStringWithSwaps(string s, vector<vector<int>>& pairs) {
        int n = s.size();
        DisjointSet dsu(n);
        for(auto it: pairs)
        {
            int u = it[0];
            int v = it[1];
            dsu.unionBySize(u,v);
        }
        vector<vector<int>> groups(n+1);
        for(int i=0; i<n; i++)
        {
            int group = dsu.findParent(i);
            groups[group].push_back(i);
        }
        vector<vector<char>> cgroups(n+1);
        for(int j=0; j<groups.size(); j++)
        {
            int m = groups[j].size();
            vector<char> temp;
            for(int i=0; i<m; i++)
            {
                temp.push_back(s[groups[j][i]]);
            }
            sort(temp.begin(), temp.end(), greater<>());
            cgroups[j] = temp;
        }
        string ans="";
        for(int i=0; i<n; i++)
        {
            int group = dsu.findParent(i);
            char curr = cgroups[group].back();
            cgroups[group].pop_back();
            ans += curr;
        }
        return ans;
    }
};
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