Building Teams

#include <cstdio>
#include <iostream>
#include <queue>
#include <utility>
#include <vector>

using namespace std;

// Depth first search
void dfs(int s, bool visited[], vector<int> adj[]) {
    if (visited[s]) {
        return;
    };
    visited[s] = true;
    for (auto u: adj[s]) {
        dfs(u, visited, adj);
    }
}

int main (int argc, char *argv[]) {
    int n, m;
    cin >> n >> m;
    vector<pair<int, int>> friends(m);
    for (int i = 0; i < m; i++) {
        cin >> friends[i].first >> friends[i].second;
    }
    // 0 is not included in cities
    vector<int> adj[n + 1];
    bool visited[n + 1];
    /*bool color[n + 1];*/
    for (int i = 0; i < n + 1; i++) {
        visited[i] = false;
    }

    // Add roads to adjacent structure
    for (int j = 0; j < m; j++) {
        adj[friends[j].first].push_back(friends[j].second);
        adj[friends[j].second].push_back(friends[j].first);
    }

    queue<int> q;
    int distance[n + 1];

    distance[1] = 0;
    q.push(1);

    /*while (!q.empty()) {*/
    /*    int s = q.front(); q.pop();*/
    /**/
    /*    for (auto u : adj[s]) {*/
    /*        if (visited[u]) continue;*/
    /*        visited[u] = true;*/
    /*        distance[u] = distance[s]+1;*/
    /*        q.push(u);*/
    /*    }*/
    /*}*/

    int k = 1;
    /*int vertices = 0;*/
    /*int edges = 0;*/
    vector<int> color(n+1, 0);
    while (!visited[k]) {
        visited[k] = true;
        color[k] = 0;
        while (!q.empty()) {
            int s = q.front(); q.pop();
            /*vertices++;*/
            /*color[s] = 1;*/

            for (auto u : adj[s]) {
                if (visited[u]) {
                    if (color[s] == color[u]) {
                        cout << "IMPOSSIBLE";
                        return 0;
                    }
                };
                visited[u] = true;
                distance[u] = distance[s]+1;
                color[u] = 1 - color[s];
                q.push(u);
                /*edges++;*/
            }
        }

        /*cout << vertices << " " << edges << "\n";*/
        /*if (edges > vertices - 1) {*/
        /*    cout << "IMPOSSIBLE";*/
        /*    return 0;*/
        /*}*/
        /*edges = 0;*/
        /*vertices = 0;*/

        // find next unconnected component
        for (int i = k; i < n + 1; i++) {
            if (!visited[i]) {
                k = i;
                q.push(i);
                break;
            }
        }
    }

    for (int i = 1; i < n + 1; i++) {
        if (distance[i] % 2) {
            cout << "1 ";
        } else {
            cout << "2 ";
        }
    }
    cout << "\n";

    /*for (int a = 0; a < n + 1; a++) {*/
    /*    cout << a << ": " << visited[a] << "\n";*/
    /*}*/

    /*std::cout << added << "\n";*/
    /*for (auto u: added_edges) {*/
    /*    cout << u - 1 << " " << u << "\n";*/
    /*}*/
    return 0;
}

Test 1

Verdict: TIME LIMIT EXCEEDED

Test 2

Verdict: TIME LIMIT EXCEEDED

Test 3

Verdict: TIME LIMIT EXCEEDED

Test 4

Verdict: TIME LIMIT EXCEEDED

Test 5

Verdict: ACCEPTED

Test 6

Verdict: TIME LIMIT EXCEEDED

Test 7

Verdict: TIME LIMIT EXCEEDED

Test 8

Verdict: TIME LIMIT EXCEEDED

Test 9

Verdict: TIME LIMIT EXCEEDED

Test 10

Verdict: ACCEPTED

Test 11

Verdict: TIME LIMIT EXCEEDED

Test 12

Verdict: ACCEPTED