Building Teams

input/code.cpp: In function 'int main()':
input/code.cpp:48:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   48 |     for (int i = 1; i < colours.size(); ++i) {
      |                     ~~^~~~~~~~~~~~~~~~
input/code.cpp:50:18: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   50 |         if (i +1 != colours.size())
      |             ~~~~~^~~~~~~~~~~~~~~~~

#include <iostream>
#include <vector>
#include <algorithm>
#include <bits/stdc++.h>
using namespace std;

void dfs_bipartite(int node, int new_col, const vector<vector<int>>& friends, vector<int>& colours) {
    colours[node] = new_col;
    for (int neighbor : friends[node]) {
        if (!colours[neighbor]) {
            if (new_col == 1)
                dfs_bipartite(neighbor, 2, friends, colours);
            else 
                dfs_bipartite(neighbor, 1, friends, colours);
        }
        else if (colours[neighbor] && colours[neighbor] == colours[node]){
            cout << "IMPOSSIBLE" << endl;
            exit(1);
        }
    }
}

int main() {
    
    int n, m;

    cin >> n >> m;

    vector< vector<int> > friends = vector<vector<int> >(n+1);
    for (int i = 0; i < m; ++i)
    {
        int aux1, aux2;

        cin >> aux1 >> aux2;

        friends[aux1].push_back(aux2);
        friends[aux2].push_back(aux1);
    }

    vector<int> colours(n + 1, 0);

    for (int i = 1; i <= n; ++i) {
        if (!colours[i]) {
            dfs_bipartite(i, 1, friends, colours);
        }
    }

    for (int i = 1; i < colours.size(); ++i) {
        cout << colours[i];
        if (i +1 != colours.size())
            cout << " ";
    }
    cout << endl;

}

Test 1

Verdict: ACCEPTED

Test 2

Verdict: ACCEPTED

Test 3

Verdict: ACCEPTED

Test 4

Verdict: ACCEPTED

Test 5

Verdict: RUNTIME ERROR

Test 6

Verdict: ACCEPTED

Test 7

Verdict: ACCEPTED

Test 8

Verdict: ACCEPTED

Test 9

Verdict: ACCEPTED

Test 10

Verdict: RUNTIME ERROR

Test 11

Verdict: RUNTIME ERROR

Test 12

Verdict: RUNTIME ERROR