Fragile network

input/code.cpp: In function 'int main()':
input/code.cpp:49:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::pair<int, int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   49 |     for (int i = 0; i < p.size(); i++) {
      |                     ~~^~~~~~~~~~

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

using namespace std;

int main() {
    int n;
    cin >> n;
    vector<vector<int>> g(n + 1);
    vector<pair<int, int>> p;

    for (int i = 0; i < n - 1; i++) {
        int a, b;
        cin >> a >> b;
        g[a].push_back(b);
        g[b].push_back(a);
    }

    queue<int> critical;
    queue<int> normal;
    for (int i = 1; i <= n; i++) {
        vector<int> adj = g[i];
        if (adj.size() <= 1) critical.push(i);
        else normal.push(i);
    }
    while (!critical.empty()) {
        int crrnt = critical.front();
        critical.pop();

        if (!critical.empty()) {
            int conn = critical.front();
            critical.pop();
            g[crrnt].push_back(conn);
            g[conn].push_back(crrnt);
            p.push_back({crrnt, conn});
        } else {
            int conn = normal.front();
            normal.push(crrnt);
            g[crrnt].push_back(conn);
            g[conn].push_back(crrnt);
            p.push_back({crrnt, conn});
        }
    }
    
    cout << p.size() << endl;
    for (int i = 0; i < p.size(); i++) {
        cout << p[i].first << ' ' << p[i].second << endl;
    }

    // vector<vector<pair<int, int> > > path(n, vector<pair<int, int> >(m));
}

Test 1

Verdict: ACCEPTED

Test 2

Verdict: ACCEPTED

Test 3

Verdict: ACCEPTED

Test 4

Verdict: ACCEPTED

Test 5

Verdict: WRONG ANSWER

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: WRONG ANSWER

Test 13

Verdict: WRONG ANSWER

Test 14

Verdict: WRONG ANSWER

Test 15

Verdict: WRONG ANSWER

Test 16

Verdict: WRONG ANSWER

Test 17

Verdict: WRONG ANSWER

Test 18

Verdict: WRONG ANSWER

Test 19

Verdict: ACCEPTED

Test 20

Verdict: WRONG ANSWER

Test 21

Verdict: ACCEPTED