Building Teams

input/code.cpp: In function 'bool dfs(int, std::vector<std::vector<int> >&, std::vector<int>&)':
input/code.cpp:12:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   12 |     for (int i = 0; i < adj[startIndex].size(); i++)
      |                     ~~^~~~~~~~~~~~~~~~~~~~~~~~
input/code.cpp: In function 'int main()':
input/code.cpp:46:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   46 |     for (int i = 0; i < teams.size(); i++)
      |                     ~~^~~~~~~~~~~~~~
input/code.cpp:58:27: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   58 |         for (int i = 0; i < teams.size() - 1; i++)
      |                         ~~^~~~~~~~~~~~~~~~~~

// Online C++ compiler to run C++ program online
#include <iostream>
#include <algorithm>
#include <vector>

using namespace std;

bool dfs(int startIndex, vector<vector<int>>& adj, vector<int>& teams)
{
    int other = teams[startIndex] == 1 ? 2 : 1;

    for (int i = 0; i < adj[startIndex].size(); i++)
    {
        if (teams[adj[startIndex][i]] == 0)
        {
            teams[adj[startIndex][i]] = other;
            if (!dfs(adj[startIndex][i], adj, teams))
                return false;
        }
        else if (teams[adj[startIndex][i]] == teams[startIndex])
        {
            return false;
        }
    }
    
    return true;
}

int main() {
    // Write C++ code here
    int n, m; // Number of pupils, friendships
    std::cin >> n >> m;
    
    vector<vector<int>> adj = vector<vector<int>>(n, vector<int>());
    
    for (int i = 0; i < m; i++)
    {
        int a, b;
        std::cin >> a >> b;
        adj[a-1].push_back(b-1);
        adj[b-1].push_back(a-1);
    }
    
    vector<int> teams = vector<int>(n, 0);
    bool valid = true;
    for (int i = 0; i < teams.size(); i++)
        if (teams[i] == 0)
        {
            teams[i] = 1;
            valid = dfs(i, adj, teams);
            if (!valid)
                break;
        }
    
    if (valid)
    {
        // Print array
        for (int i = 0; i < teams.size() - 1; i++)
            std::cout << teams[i] << " ";
        std::cout << teams[teams.size() - 1];
    }
    else
    {
        std::cout << "IMPOSSIBLE";
    }
    

    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