<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:
    vector<int> parents;
    vector<int> ranks;
    int uffind(int a){
        if(parents[a] == a)return a;
        parents[a] = uffind(parents[a]);
        return parents[a];
    }
    void ufjoin(int a, int b){
        int aroot{uffind(a)}, broot{uffind(b)};
        if(aroot == broot)return;
        if(ranks[aroot] > ranks[broot]){
            ranks[aroot] += ranks[broot];
            parents[broot] = aroot; 
        }
        else{
            ranks[broot] += ranks[aroot];
            parents[aroot] = broot; 
        }
    }

    string smallestStringWithSwaps(string s, vector<vector<int>>& pairs) {
        const int S{(int)s.size()};
        parents.resize(S);
        ranks.resize(S, 1);
        iota(parents.begin(), parents.end(),0);
        for(vector<int>& p : pairs) ufjoin(p[0], p[1]);
        vector<vector<int>> d(S);
        for(int i = 0; i < S; i++) d[uffind(i)].push_back(i);
        vector<vector<int>> dcpy{d};
        for(int i = 0; i < S; i++){
            sort(dcpy[i].begin(), dcpy[i].end(),[&s](int a, int b){return s[a] < s[b];});
        }
        string res{s};
        for(int i = 0; i< S; i++){
            for(int j = 0; j < d[i].size(); j++){
                res[d[i][j]] = s[dcpy[i][j]];
            }
        }
        return res;

    }
};
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