Building Teams

input/code.cpp: In function 'int main()':
input/code.cpp:19:13: warning: unused variable 'shop' [-Wunused-variable]
   19 |         int shop;
      |             ^~~~
input/code.cpp:48:24: warning: variable 'it_teams1' set but not used [-Wunused-but-set-variable]
   48 |     set<int>::iterator it_teams1 = team1.begin();
      |                        ^~~~~~~~~
input/code.cpp:49:24: warning: variable 'it_teams2' set but not used [-Wunused-but-set-variable]
   49 |     set<int>::iterator it_teams2 = team2.begin();
      |                        ^~~~~~~~~

#include <string>
#include <iostream>
#include <set>

using namespace std;

int main()
{
    int n_pups, n_friendships;
    cin >> n_pups >> n_friendships;
    set<int> team1;
    set<int> team2;
    int pup1, pup2;
    bool possible = true;

    for(int i = 0; i < n_friendships; ++i)
    {
        cin >> pup1 >> pup2;
        int shop;
        if(team1.count(pup1))
        {
            if(!team1.count(pup2)) team1.insert(pup1), team2.insert(pup2);
            else {possible = false; break;}
        }
        else if(team2.count(pup1))
        {
            if(!team2.count(pup2)) team2.insert(pup1), team1.insert(pup2);
            else {possible = false; break;}
        }
        else if(team1.count(pup2))
        {
            if(!team1.count(pup1)) team1.insert(pup2), team2.insert(pup1);
            else {possible = false; break;}
        }
        else if(team2.count(pup2))
        {
            if(!team1.count(pup1)) team2.insert(pup2), team1.insert(pup1);
            else {possible = false; break;}
        }
        else
        {
            team1.insert(pup1);
            team2.insert(pup2);
        }
    }


    set<int>::iterator it_teams1 = team1.begin();
    set<int>::iterator it_teams2 = team2.begin();

    if(possible)
    {    for(int i = 1; i <= n_pups; ++i)
        {
            if(team1.count(i)) printf("1 ");
            else printf("2 ");
        }
        printf("\n");
    }
    else {
        printf("IMPOSSIBLE\n");
    }
    return 0;
}

Test 1

Verdict: WRONG ANSWER

Test 2

Verdict: WRONG ANSWER

Test 3

Verdict: ACCEPTED

Test 4

Verdict: WRONG ANSWER

Test 5

Verdict: ACCEPTED

Test 6

Verdict: WRONG ANSWER

Test 7

Verdict: WRONG ANSWER

Test 8

Verdict: WRONG ANSWER

Test 9

Verdict: WRONG ANSWER

Test 10

Verdict: ACCEPTED

Test 11

Verdict: ACCEPTED

Test 12

Verdict: ACCEPTED