Connect cities

input/code.cpp: In function 'int main()':
input/code.cpp:60:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   60 |     for (int i = 1; i < news.size(); ++i) cout << news[i - 1] << ' ' << news[i] << endl;
      |                     ~~^~~~~~~~~~~~~

#include <iostream>
#include <vector>
#include <queue>
 
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);
 
        cout << "x0" << endl;
 
 
    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;
        int end = -1;
        
        queue<int> q;
        q.push(start);
 
        while(not q.empty()) {
            int current = q.front();
            q.pop();
 
            for (int node : roads[current]) {
                if (!visited[node]) {
                    end = current;
                    q.push(node);
                    visited[node] = true;
                }
            }
        }
        if (end != -1) news.push_back(end);
 
        
 
 
    }
 
    cout << news.size()/2 << endl;
 
    for (int i = 1; i < news.size(); ++i) cout << news[i - 1] << ' ' << news[i] << endl;
 
}

Test 1

Verdict: WRONG ANSWER

Test 2

Verdict: WRONG ANSWER

Test 3

Verdict: ACCEPTED

Test 4

Verdict: WRONG ANSWER

Test 5

Verdict: ACCEPTED

Test 6

Verdict: WRONG ANSWER

Test 7

Verdict: WRONG ANSWER

Test 8

Verdict: WRONG ANSWER

Test 9

Verdict: WRONG ANSWER

Test 10

Verdict: WRONG ANSWER

Test 11

Verdict: WRONG ANSWER

Test 12

Verdict: WRONG ANSWER