<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 DSU {
private:
    vector<int> parents;
    vector<int> sizes;
public:
    DSU(int n) {
        parents.resize(n);
        iota(parents.begin(), parents.end(), 0);
        sizes.assign(n, 1);
    }

    int find(int a) {
        if (parents[a] != a) {
            return parents[a] = find(parents[a]);
        }
        return parents[a];
    }

    void join(int smaller, int larger) {
        smaller = find(smaller);
        larger = find(larger);
        if (smaller != larger) {
            if (sizes[smaller] > sizes[larger]) {
                swap(smaller, larger);
            }
            sizes[larger] += sizes[smaller];
            parents[smaller] = larger;
        }
    }

    vector<vector<int>> getSets() {
        unordered_map<int, vector<int>> sets;
        for (int i = 0; i < parents.size(); ++i) {
            sets[find(i)].push_back(i);
        }
        vector<vector<int>> ret;
        for (auto& kv : sets) {
            ret.push_back(kv.second);
        }
        return ret;
    }

};
class Solution {
public:
    string smallestStringWithSwaps(string s, vector<vector<int>>& pairs) {
        int n = pairs.size();
        DSU dsu(s.length());
        for (auto& v : pairs) {
            dsu.join(v[0], v[1]);
        }
        vector<vector<int>> sets = dsu.getSets();
        for (auto& set : sets) {
            vector<char> chars;
            for (int i : set) {
                chars.push_back(s[i]);
            }
            sort(chars.begin(), chars.end());
            sort(set.begin(), set.end());
            for (int i = 0; i < set.size(); ++i) {
                s[set[i]] = chars[i];
            }
        }
        return s;
    }
};
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