Building Teams

#include<bits/stdc++.h>
using namespace std;
vector<vector<int>> adj;
vector<int> team;
bool dfs(int node, int current_team) {
    team[node] = current_team;
    for (int neighbor : adj[node]) {
        if (team[neighbor] == 0) {
            if (!dfs(neighbor, 3 - current_team)) return false;
        } else if (team[neighbor] == current_team) {
            return false;
        }
    }
    return true;
}
int main() {
    int n, m;
    cin >> n >> m;
    adj.resize(n + 1);
    team.resize(n + 1, 0);
    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) {
        if (team[i] == 0) {
            if (!dfs(i, 1)) {
                cout << "IMPOSSIBLE\n";
                return 0;
            }
        }
    }
    for (int i = 1; i <= n; ++i) {
      cout << team[i] << " ";
    }
    cout<<"\n";
}

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