Building Teams

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

using namespace std;

int main() {
    int n, m;
    cin >> n >> m;

    vector<int> dist(n+1,0);

    vector<pair<int,int>> friendships;
    vector<vector<int>> adj(n+1);
    

    for(int i = 0; i < m; i++) {
        int a, b;
        cin >> a >> b;
        
        adj[a].push_back(b);
        adj[b].push_back(a);
    }
    
    vector<bool> visited1(n+1, false);
    vector<bool> visited2(n+1, false);


        int start = 1;
        vector<int> team (n+1, 0);

        queue<int> q1;
        queue<int> q2;
        visited1[start] = true;
        q1.push(start);
        team[start] = 1;


        /*while (!q1.empty()) {
            int s = q1.front(); q1.pop();
            for (auto u : adj[s]) {
                if (visited1[u] && team[u] == team[s]) {
                    cout << "IMPOSSIBLE" << endl;
                    return 0;
                }
                visited1[u] = true;
                q1.push(u);
                if(team[s] == 1) team[u] = 2;
                else team[u] = 1;
                cout << "Team 1: " << u << endl;
            }
        }

        for(int i = 1; i <= n; i++) {
            if(!visited1[i]) {
                start = i;
                break;
            }
            if(visited1[i] && i == n) {
                start = 0;
                break;
            }
        }
        if(start != 0){
team[start] = 1;
        while (!q2.empty()) {
            int s = q2.front(); q2.pop();
            for (auto u : adj[s]) {
                if (visited1[u]) continue;
                visited2[u] = true;
                q2.push(u);
                team[u] = 2;
            }
        }
        }*/
        

    vector<bool> visited(n+1, false);
    
        start = 1;
    for(int i = 1; i <= 2; i++) {
        queue<int> q;

        visited[start] = true;
        q.push(start);

        while (!q.empty()) {
            int s = q.front(); q.pop();
            for (auto u : adj[s]) {
                if (team[u] == team[s]) {
                    cout << "IMPOSSIBLE" << endl;
                    return 0;
                }
                else if(visited[u]) continue;
                visited[u] = true;
                q.push(u);
                if(team[s] == 1) team[u] = 2;
                else team[u] = 1;
            }
        }

        for(int i = 1; i <= n; i++) {
            if(!visited[i]) {
                
                start = i;
                break;
            }
        }
        /*for( int i = 1; i <= n; i++) {
            cout << i << ": " << visited[i] <<endl;
        }*/
    


}
        


    
    //sort(friendships.begin(), friendships.end());

       /*if(dist[friendships[i].first] == 1 && dist[friendships[i].second] == 0) {
           dist[friendships[i].second] = 2;
       }
       else if(dist[friendships[i].first] == 2 && dist[friendships[i].second] == 0) {
           dist[friendships[i].second] = 1;
       }
       else if(dist[friendships[i].first] == 0 && dist[friendships[i].second] == 1) {
           dist[friendships[i].first] = 2;
       }
       else if(dist[friendships[i].first] == 0 && dist[friendships[i].second] == 2) {
           dist[friendships[i].first] = 1;
       }
       else if(dist[friendships[i].first] == 0 && dist[friendships[i].second] == 0) {
           dist[friendships[i].first] = 1;
           dist[friendships[i].second] = 2;
           //cout << friendships[i].first << " " << friendships[i].second << endl;

       }
       else if(dist[friendships[i].first] == 2 && dist[friendships[i].second] == 1) {
           cout << "IMPOSSIBLE" << endl;
           return 0;
       }
       else if(dist[friendships[i].first] == 1 && dist[friendships[i].second] == 2) {
           cout << "IMPOSSIBLE" << endl;
           return 0;
       }*/
       
    

    for(int i = 1; i <= n; i++) {
        if(team[i] == 0 || team[i] == 1) cout << 1 << " ";
        else cout << 2 << " ";
        //cout << dist[i] << endl;
    }

}

Test 1

Verdict: ACCEPTED

Test 2

Verdict: ACCEPTED

Test 3

Verdict: ACCEPTED

Test 4

Verdict: ACCEPTED

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: ACCEPTED

Test 11

Verdict: ACCEPTED

Test 12

Verdict: ACCEPTED