Building Teams

#include <bits/stdc++.h>

using namespace std;
const int N = 100005;
vector<int> adj[N];
bool visited[N];
vector<int> team(N);

int dfs(int s) {
	if (visited[s]) return 0;
	visited[s] = true;
	int vis = 0;
	int ts = team[s];
	if (ts == 0) {
		team[s] = ts = 1;
	}
	for (int nb : adj[s]) {
		if (team[nb] == 0) {
			team[nb] = 3-ts;
		}
		if (team[nb] == ts && ts != 0) {
			cout << "IMPOSSIBLE";
			return -1;
		}
		int t = dfs(nb);
		if (t == -1) return -1;
		vis += t;
	}
	return vis + 1;
}

int main() {
	int n, m, a, b;
	cin >> n >> m;
	for (int i=0; i<m; i++) {
		cin >> a >> b;
		adj[a].push_back(b);
		adj[b].push_back(a);
	}
	int dis = 0;
	int vis = 0;
	vector<int> rc;
	for (int i=1; i<=n; i++) {
		int v = dfs(i);
		if (v == -1) {
			return 0;
		}
		if (v) {
			dis += 1;
			vis += v;
			rc.push_back(i);
		}
		if (vis == n) break;
	}

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