<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 n;

    vector<vector<int>> adjs;

    void initGraph(int n)
    {
        adjs = vector<vector<int>>(n);
    }

    void addEdge(int u, int v)
    {
        adjs[u].push_back(v);
        adjs[v].push_back(u);
    }

    vector<bool> visited;

    vector<int> bfs(int start)
    {
        vector<int> components;
        std::queue<int> q;
        q.push(start);
        visited[start] = true;

        while(!q.empty())
        {
            auto u = q.front();
            q.pop();

            components.push_back(u);

            for(auto v: adjs[u] )
            {
                if(!visited[v])
                {
                    visited[v] = true;
                    q.push(v);
                }
            }
        }

        return components;
    }

    string smallestStringWithSwaps(string s, vector<vector<int>>& pairs) {
        n = s.size();

        visited = vector<bool> (n, false);


        initGraph(n);

        for(auto pair: pairs)
        {
            int u = pair[0];
            int v = pair[1];

            addEdge(u, v);
        }

        for(int i = 0; i < n; ++i)
        {
            if(!visited[i])
            {
                vector<int> component = bfs(i);

                vector<char> chars;
                // Thêm ký tự tương ứng từ chuỗi `s` vào vector `chars`
                for (auto idx : component) {
                    chars.push_back(s[idx]);
                }

                // Sắp xếp các chỉ số và ký tự
                sort(component.begin(), component.end());
                sort(chars.begin(), chars.end());

                // Đặt lại các ký tự đã sắp xếp vào vị trí tương ứng trong chuỗi `s`
                for (int j = 0; j < component.size(); ++j) {
                    int idx = component[j];
                    s[idx] = chars[j];
                }

            }
        }

        return s;
    }
};

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