Connect cities

input/code.cpp: In function 'int main()':
input/code.cpp:56:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   56 |     for (int i = 1; i < news.size(); ++i) cout << news[i - 1] + 1 << ' ' << news[i] + 1 << endl;
      |                     ~~^~~~~~~~~~~~~

#include <iostream>
#include <queue>
#include <vector>

using namespace std;

int main() {
    int c, r;
    cin >> c >> r;

    // vector<vector<bool> > roads(c, vector<bool>(c, false));
    vector<bool> visited(c, false);

    vector<vector<int> > roads(c);

    for (int i = 0; i < r; i++) {
        int city1, city2;
        cin >> city1 >> city2;

        --city1;
        --city2;

        roads[city1].push_back(city2);
        roads[city2].push_back(city1);
    }

    vector<int> news;
    for (int i = 0; i < c; ++i) {
        int start = i;



        if (not visited[i]) {
            news.push_back(start);

            queue<int> q;
            q.push(start);

            while (not q.empty()) {
                int current = q.front();
                q.pop();

                for (int node : roads[current]) {
                    if (!visited[node]) {
                        q.push(node);
                        visited[node] = true;
                    }
                }
            }
        }
    }

    cout << news.size() - 1<< endl;

    for (int i = 1; i < news.size(); ++i) cout << news[i - 1] + 1 << ' ' << news[i] + 1 << endl;
}

Test 1

Verdict: ACCEPTED

Test 2

Verdict: ACCEPTED

Test 3

Verdict: ACCEPTED

Test 4

Verdict: ACCEPTED

Test 5

Verdict: ACCEPTED

Test 6

Verdict: ACCEPTED

Test 7

Verdict: ACCEPTED

Test 8

Verdict: ACCEPTED

Test 9

Verdict: ACCEPTED

Test 10

Verdict: ACCEPTED

Test 11

Verdict: ACCEPTED

Test 12

Verdict: ACCEPTED