Building Teams

#include <bits/stdc++.h>
#define ll long long
#define ii pair<int,int>
#define iii pair<int,pair<int,int>>
#define pb push_back
using namespace std;
const int N=1e5+3;
const int M=2e5+3;
int n,m;
vector<int>g[N];
int vis[N];
bool bfs(int start) {
    vis[start]=1;
    queue<int>q;
    q.push(start);
    while (!q.empty()) {
        int node=q.front();
        q.pop();
        for (auto u:g[node]) {
            if (vis[node]==1) {
                if (vis[u]==0) {
                    vis[u]=2;
                    q.push(u);
                }
                else if (vis[u]==1) {
                    return false;
                }
            }
            if (vis[node]==2) {
                if (vis[u]==0) {
                    vis[u]=1;
                    q.push(u);
                }else if (vis[u]==2) {
                    return false;
                }
            }
        }
    }
    return true;
}
int main() {
    ios::sync_with_stdio(0); cin.tie(0);
    cin >> n >> m;
    for (int i=1; i<=n; i++) {
        vis[i]=0;
    }
    for (int i=1; i<=m; i++) {
        int u,v;
        cin >> u >> v;
        g[u].pb(v);
        g[v].pb(u);
    }
    bool ans=true;
    for (int i=1; i<=n; i++) {
        if (vis[i]==0) {
            if (bfs(i)==false) {
                ans=false;
                break;
            }
        }
    }
    if (ans) {
        for (int i=1; i<=n; i++) cout << vis[i] << ' ';
        return 0;
    }
    cout << "IMPOSSIBLE";
    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