Connect cities

input/code.cpp:10:19: warning: overflow in conversion from 'double' to 'int' changes value from '4.0e+18' to '2147483647' [-Woverflow]
   10 | const int LLINF = 4e18; // 4*10^18 is < 2^63-1
      |                   ^~~~
input/code.cpp: In function 'int main()':
input/code.cpp:58:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   58 |     for (int i = 0; i < comp.size()-1; i++) {
      |                     ~~^~~~~~~~~~~~~~~

#include <bits/stdc++.h>
using namespace std;

#define rep(i, a, b) for(int i=a; i< (b); ++i)
#define all(x) begin(x), end(x)
#define sz(x) (int)(x).size()
typedef long long ll;

const int INF = 1e9; // 10^9 = 1B is < 2^31-1
const int LLINF = 4e18; // 4*10^18 is < 2^63-1
const double EPS = 1e-9;
const ll MOD = 1e9+7;

const int N=1e5+10;

vector<int> adj[N];
bool vis[N];

void dfs(int node, int prev) {
    if(vis[node]) return;
    vis[node]=true;

    for(auto &w:adj[node]) {
        if(w==prev) continue;
        dfs(w, node);
    }
}

int main() {
    cin.tie(0)->sync_with_stdio(0);
    cin.exceptions(cin.failbit);
    
    int n, m; std::cin >> n >> m;

    for (int i = 1; i <= n; i++) vis[i]=false;
    

    for (int i = 0; i < m; i++) {
        int a,b; std::cin >> a >> b;
        adj[a].push_back(b);
        adj[b].push_back(a);
    }


    vector<int> comp;

    for (int i = 1; i <= n; i++) {
        if(!vis[i]) {
            comp.push_back(i);
            dfs(i, -1);
        }
    }



    std::cout << comp.size()-1 << std::endl;

    for (int i = 0; i < comp.size()-1; i++) {
        std::cout << comp[i] << " " << comp[i+1] << endl;
    }
    


    return 0;
}

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