<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
{
private:
    int size;
    vector<int> rank;
    vector<int> root;
public:
    DisjointSet(int nSize) :
        size(nSize),
        rank(nSize, 1)
    {
        for (int n = 0; n < nSize; n++)
        {
            root.push_back(n);
        }
    }
    
    int djsFind(int node)
    {
        vector<int> visited;
        while (node != root[node])
        {
            visited.push_back(node);
            node = root[node];
        }
        for (int n : visited)
        {
            root[n] = node;
        }
        return node;
    }
    
    void djsUnion(int left, int right)
    {
        int leftRoot = djsFind(left);
        int rightRoot = djsFind(right);
        
        if (leftRoot == rightRoot)
        {
            return;
        }
        else if (rank[leftRoot] > rank[rightRoot])
        {
            root[rightRoot] = leftRoot;
            size--;
        }
        else if (rank[rightRoot] > rank[leftRoot])
        {
            root[leftRoot] = rightRoot;
            size--;
        }
        else
        {
            root[leftRoot] = rightRoot;
            rank[rightRoot]++;
            size--;
        }
    }
    
    void getSets(unordered_map<int, vector<int>> & sets)
    {
        for (int i = 0; i < root.size(); i++)
        {
            int iRoot = djsFind(i);
            sets[iRoot].push_back(i);
        }
    }
};

class Solution {
public:
    string smallestStringWithSwaps(string s, vector<vector<int>>& pairs) {
        DisjointSet djs(s.length());
        for (vector<int> & p : pairs)
        {
            djs.djsUnion(p[0], p[1]);
        }
        
        unordered_map<int, vector<int>> sets;
        djs.getSets(sets);
        
        for (auto it = sets.begin(); it != sets.end(); it++)
        {
            vector<int> & nodes = it->second;
            
            sort(nodes.begin(), nodes.end());
            
            vector<char> chars;
            for (int n : nodes)
            {
                chars.push_back(s[n]);
            }
            sort(chars.begin(), chars.end());
            
            for (int i = 0; i < nodes.size(); i++)
            {
                s[nodes[i]] = chars[i];
            }
        }
        
        return s;
    }
};
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