Building Teams

#include <bits/stdc++.h>

using namespace std;
#define ll long long

bool dfs(vector<vector<int>>& g, int u, int color, vector<int>& colors) {

    if (colors[u] != -1) {
        return colors[u] == color;
    }

    colors[u] = color;
    for (auto &v : g[u]) {
        if (!dfs(g, v, 3 - color, colors)) {
            return false;
        }
    }

    return true;

}



int main() {

    int n, m;
    cin >> n >> m;

    vector<vector<int>> g(n+1);
    while (m--) {
        int a, b;
        cin >> a >> b;
        g[a].push_back(b);
        g[b].push_back(a);
    }
    
    
    // cout << "hye" << endl;
    vector<int> colors(n+1, -1);
    bool possible = true;
    for (int i = 1; i <= n; i++) {
        if (colors[i] != -1) continue;
        bool v = dfs(g, i, 1, colors);
        if (!v) possible = false;
    }

    if (possible) {
        for (int i = 1; i <= n; i++) {
            if (i > 1) cout << " ";
            cout << colors[i];
        }
        cout << endl;
    } else {
        cout << "IMPOSSIBLE" << endl;
    }

}

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