<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>

#include <vector>
#include <string>
#include <queue>
#include <algorithm>

using namespace std;

class Solution {
public:
    void bfs(int start, vector<vector<int>>& adj, vector<bool>& visited, vector<int>& component) {
        queue<int> q;
        q.push(start);
        visited[start] = true;

        while (!q.empty()) {
            int node = q.front();
            q.pop();
            component.push_back(node);

            for (int neighbor : adj[node]) {
                if (!visited[neighbor]) {
                    visited[neighbor] = true;
                    q.push(neighbor);
                }
            }
        }
    }
    
    string smallestStringWithSwaps(string s, vector<vector<int>>& pairs) {
        int n = s.length();
        vector<vector<int>> adj(n);
        
        // Xây dựng đồ thị với các cạnh từ cặp hoán đổi
        for (const auto& pair : pairs) {
            adj[pair[0]].push_back(pair[1]);
            adj[pair[1]].push_back(pair[0]);
        }
        
        vector<bool> visited(n, false);
        
        // Xử lý từng thành phần liên thông trong đồ thị
        for (int i = 0; i < n; ++i) {
            if (!visited[i]) {
                vector<int> component;
                bfs(i, adj, visited, component);
                
                // Sắp xếp các chỉ số và ký tự tương ứng
                string chars;
                for (int index : component) {
                    chars += s[index];
                }
                sort(component.begin(), component.end());
                sort(chars.begin(), chars.end());
                
                // Đặt lại các ký tự vào chuỗi ban đầu theo thứ tự nhỏ nhất
                for (int j = 0; j < component.size(); ++j) {
                    s[component[j]] = chars[j];
                }
            }
        }
        
        return s;
    }
};

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