Connect cities

#include<iostream>
#include<vector>
#include<queue>
using namespace std;
int not_visited(const vector<bool> & visited){
    int n = visited.size();
    for(int i = 0;i < n; ++i){
        if(visited[i] == false)
            return i;
    }
    return -1;
}
void dfs(int s,vector<int> adj[],vector<bool> & visited, vector<pair<int,int>> &new_roads, 
int vist, int N ) {
//if (visited[s]) return;
    if(visited[s] == true and vist == N) return;
    else if(visited[s] == true){
        visited[s] = true;
        int u = not_visited(visited);
        if(u == -1) return;
        new_roads.push_back({s,u});
        dfs(u,adj,visited,new_roads,vist,N);
        return;
    }
    else{
        ++vist;
        visited[s] = true;
        /*cout<<"----------------------"<<endl;
        cout<<new_roads.size()<<endl;
        for(auto p: new_roads)
        cout<<p.first<<" "<<p.second<<endl;
        cout<<"----------------------"<<endl;*/
        if(adj[s].size()==0){
            int u = not_visited(visited);
            if(u == -1) return;
            new_roads.push_back({s,u});
            dfs(u,adj,visited,new_roads,vist,N);
            return;
        }
        // process node s
        else{
            for (auto u: adj[s]) {
                dfs(u,adj,visited,new_roads,vist,N);
            }   
        }
    }
}

int main(){
    int n, m;
    cin >> n >> m;
    vector<int> adj[n];
    vector<bool> visited(n);
    int vist = 0;
    vector<pair<int,int>> new_roads;
    for(int i = 0; i < m; ++i){
        int a,b;
        cin >> a >> b;
        --a;
        --b;
        adj[a].push_back(b);
        adj[b].push_back(a);
    }
    int act = 0;

    dfs(act,adj,visited,new_roads,vist,n);
    cout<<new_roads.size()<<endl;
    for(auto p: new_roads)
        cout<<p.first+1<<" "<<p.second+1<<endl;
}

Test 1

Verdict: WRONG ANSWER

Test 2

Verdict: WRONG ANSWER

Test 3

Verdict: WRONG ANSWER

Test 4

Verdict: WRONG ANSWER

Test 5

Verdict: WRONG ANSWER

Test 6

Verdict: TIME LIMIT EXCEEDED

Test 7

Verdict: TIME LIMIT EXCEEDED

Test 8

Verdict: TIME LIMIT EXCEEDED

Test 9

Verdict: TIME LIMIT EXCEEDED

Test 10

Verdict: TIME LIMIT EXCEEDED

Test 11

Verdict: TIME LIMIT EXCEEDED

Test 12

Verdict: WRONG ANSWER