Building Teams

#include <bits/stdc++.h>

using namespace std;

const int N = 1e5 + 5;

int n, m;
vector<int> g[N];
int ans[N];
bool f;

void dfs(int u) {
  for (int v : g[u]) {
    if (ans[v] == ans[u]) {
      f = false;
    } else if (ans[v] == 0) {
      ans[v] = 3 ^ ans[u];
      dfs(v);
    }
  }
}

int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  cin >> n >> m;
  for (int i = 1; i <= m; i++) {
    int a, b;
    cin >> a >> b;
    g[a].emplace_back(b);
    g[b].emplace_back(a);
  }
  f = true;
  for (int i = 1; i <= n; i++) {
    if (ans[i] == 0) {
      ans[i] = 1;
      dfs(i);
    }
  }
  if (!f) {
    cout << "IMPOSSIBLE" << '\n';
    return 0;
  }
  for (int i = 1; i <= n; i++) {
    cout << ans[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