Connect cities

#include <vector>
#include <iostream>
 
using namespace std;
 
void dfs(int n, vector<bool> &visited, const vector<vector<int>> adj);
 
int main()
{
 
    int n;
    int m;
    cin >> n;
    cin >> m;
 
    vector<vector<int>> adj(n + 1);
    vector<int> components;
 
    for (int i = 0; i < m; i++)
    {
        int a, b;
        cin >> a >> b;
        adj[a].push_back(b);
        adj[b].push_back(a);
    }
 
    // cout << "Adjacencies done";
    // for (int i = 0; i < n; i++)
    // {
    //     cout << i;
    //     for (int neighbors : adja[i])
    //     {
    //         cout << neighbors << " ";
    //     }
    //     cout << "\n";
    // }
 
    vector<bool> visited(n + 1, false);
 
    for (int i = 1; i < n + 1; i++)
    {
        if (!visited[i])
        {
            components.push_back(i);
            dfs(i, visited, adj);
        }
    }
    int size = components.size();
    cout << size - 1 << "\n";
    for (int i = 1; i < size; i++)
    {
        cout << components[i - 1] << " " << components[i] << "\n";
    }
}
 
void dfs(int n, vector<bool> &visited, const vector<vector<int>> adj)
{
    // if (visited[n])
    // {
    //     return;
    // }
    visited[n] = true;
    for (int neighbor : adj[n])
    {
        if (visited[neighbor] != true)
        {
            dfs(neighbor, visited, adj);
        }
    }
}

Test 1

Verdict: ACCEPTED

Test 2

Verdict: ACCEPTED

Test 3

Verdict: ACCEPTED

Test 4

Verdict: ACCEPTED

Test 5

Verdict: ACCEPTED

Test 6

Verdict: RUNTIME ERROR

Test 7

Verdict: RUNTIME ERROR

Test 8

Verdict: RUNTIME ERROR

Test 9

Verdict: RUNTIME ERROR

Test 10

Verdict: RUNTIME ERROR

Test 11

Verdict: TIME LIMIT EXCEEDED

Test 12

Verdict: ACCEPTED