Building Teams

#include <iostream>
#include <algorithm>
#include <vector>
#include <stack>
#include <queue>
using namespace std;

bool dfs(vector<bool>& visited, vector<int>& sol, vector<vector<int>>& adjList, int node){
    if (visited[node]){
        return true;
    }

    sol[node] = 1;

    queue <int> q;
    q.push(node);

    while (!q.empty())
    {
        int u = q.front();
        q.pop();
        visited[u] = true;
        
        vector<int> neighbours = adjList[u];
        for (int neighbour : neighbours)
        {
            if (sol[neighbour] == -1)
            {
                sol[neighbour] = (sol[u] == 1)? 2 : 1;
                q.push(neighbour);
            }
            else if (sol[neighbour] == sol[u])
                return false;
        }
    }
    return true;
}

int main() {
    int n, m;
    cin >> n >> m;
    
    vector<vector<int>> adjList(n+1, vector<int>());

    for (int i = 1; i <= m; i++){
        int a, b;
        cin >> a >> b;
        adjList[a].push_back(b);
        adjList[b].push_back(a);
    }
    
    vector<int> sol(n+1, -1);
    vector<bool> visited(n+1, false);
    for (int i = 1; i <= n; i++){
        if(!dfs(visited, sol, adjList, i)){
            cout << "IMPOSSIBLE";
            return 0;
        }
    }
    
    for (int i = 1; i <= n; i++){
        cout << sol[i] << " ";
    }
    
    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