<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:
    int fn(int x, vector<int> &rn) {
        if(x==rn[x]) {
            return x;
        }
        return rn[x]=fn(rn[x],rn);
    }

    bool un(int x, int y, vector<int> &rn) {
        x=fn(x,rn);
        y=fn(y,rn);
        if(x==y) {
            return false;
        }
        rn[y]=x;
        return true;
    }
    string smallestStringWithSwaps(string s, vector<vector<int>>& pairs) {
        int n=s.size();
        vector<int> rn(n+1,0);
        for(int i=0; i<=n; i++) {
            rn[i]=i;
        }
        for(auto u:pairs) {
            un(u[0],u[1],rn);
        }
        vector<vector<int>> comps(n+1);
        for(int i=0; i<n; i++) {
            comps[fn(i,rn)].push_back(i);
        }
        string ans(n,'*');
        for(int i=0; i<n; i++) {
            if(!comps[i].empty()) {
                multiset<char> chars;
                for(auto v:comps[i]) {
                    chars.insert(s[v]);
                }
                for(auto v:comps[i]) {
                    ans[v]=*chars.begin();
                    chars.erase(chars.begin());
                }
            }
        }
        return ans;
    }
};
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