Building Teams

#include <bits/stdc++.h>
using namespace std;
#define ln "\n"
typedef long long ll;
#define fastio ios_base::sync_with_stdio(false), cin.tie(NULL)

const int MAX = 100000;
vector<int> adj[MAX+1]; 
int team[MAX +1];


bool bfs(int start){
    queue<int> q;
    q.push(start);

    team[start] = 1; 
    
    while(!q.empty()){

        int u = q.front();
        q.pop();
        
        for(int x : adj[u]){

            if(team[x] ==0){
                
                team[x] = 3 -team[u];
                q.push(x);

            }else if(team[x] == team[u]){
                
                return false;
            }
        }
    }
    
    return true;
}

int main(){
    int n, m;
    cin >> n >> m;
    
    
    for(int i = 0; i<m; i++){

        int a, b;
        cin >> a >> b;

        adj[a].push_back(b);
        adj[b].push_back(a);
    }
    
    
    for(int i = 1; i<= n;i++){
        team[i] = 0;
    }

    
    for(int i = 1; i <=n; i++){

        if(team[i] == 0){ 

            if(!bfs(i)){ 

                cout << "IMPOSSIBLE" << endl;

                return 0;
            }
        }
    }
    
    
    for(int i = 1; i<= n; i++){
        cout << team[i] << " ";
    }
    cout << 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