<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 {
public:
    string smallestStringWithSwaps(string s, vector<vector<int>>& pairs) {
        const int SIZE = s.size();
        UnionFind disjointSet(SIZE);
        
        for (vector<int> pair : pairs)
            disjointSet.quickUnion(pair[0], pair[1]);
        
        for (int i = 0; i < SIZE; i++)
            disjointSet.find(i);
        
        unordered_map<int, vector<int>> disjointSetDic;
        unordered_map<int, string> subStringDic;

        for (int i = 0; i < SIZE; i++)
        {
            disjointSetDic[disjointSet.root[i]].push_back(i);
            subStringDic[disjointSet.root[i]] += s[i];
        }
        
        for (pair<const int, string>& pair  : subStringDic)
        {
            sort(pair.second.begin(), pair.second.end());
        }
        
        for (pair<int, vector<int>> pair : disjointSetDic)
        {
            int size = pair.second.size();
            for (int i = 0; i < size; i++)
            {
                s[pair.second[i]] = subStringDic[pair.first][i];
            }
        }
        return s;
    };
private:
    class UnionFind{
    public:
        vector<int> root;
        UnionFind(int size): root(size), rank(size)
        {
            for (int i = 0; i < size; i++)
            {
                root[i] = i;
                rank[i] = 1;
            }
        }
        int find(int vertex)
        {
            if (vertex == root[vertex])
                return vertex;
            return root[vertex] = find(root[vertex]);
        }
        void quickUnion(int vertexA, int vertexB)
        {
            int rootA = find(vertexA);
            int rootB = find(vertexB);
            if (rootA != rootB)
            {
                if (rank[rootA] > rank[rootB])
                    root[rootB] = rootA;
                else if (rank[rootA] < rank[rootB])
                    root[rootA] = rootB;
                else
                {
                    root[rootB] = rootA;
                    rank[rootA]++;
                }
            }
        }
    private:
        vector<int> rank;
    };
};
60537