Building Teams

input/code.cpp: In function 'bool coloring(std::vector<int>&, std::vector<std::vector<int> >&)':
input/code.cpp:37:19: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   37 |     for(int i=0; i< color.size(); i++){
      |                  ~^~~~~~~~~~~~~~
input/code.cpp: In function 'int main()':
input/code.cpp:64:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   64 |         for(int i=0; i< color.size(); i++){
      |                      ~^~~~~~~~~~~~~~
input/code.cpp:66:17: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   66 |             if(i!=color.size()-1) cout<<" ";
      |                ~^~~~~~~~~~~~~~~~

#include <iostream>
#include <vector>
#include <stack>

using namespace std;

bool BFS(vector<int>& color, vector<vector<int>>& friends, int idx){
    stack<int> q;
 
    q.push(idx);
    color[idx] = 0;
    
 
    while(not q.empty())
    {
        int x = q.top();
        q.pop();
        for(unsigned int i=0; i<friends[x].size(); i++){
            if(color[friends[x][i]] == -1){
                if(color[x]==1) color[friends[x][i]] = 0;
                else color[friends[x][i]] = 1;
                q.push(friends[x][i]);
            }
            else if (color[friends[x][i]] == color[x])
            {
                return false;
            }
            
        }
        
    }
 
    return true;
}

bool coloring(vector<int>& color, vector<vector<int>>& friends){
    for(int i=0; i< color.size(); i++){
        if(color[i]==-1){

            if(BFS(color, friends, i) == false) return false;
        }
    }
    return true;
}

int main(){
    unsigned int n,m;
    cin >> n >> m;
 
    vector<int> color(n, -1);
    vector<vector<int>> friends(n);
 
    for(unsigned int i=0; i<m; i++){
        int a,b;
        cin >> a >> b;
        friends[a-1].push_back(b-1);
        friends[b-1].push_back(a-1);
    }

    if (coloring(color, friends)==false){
        cout<<"IMPOSSIBLE";
    }
    else{
        for(int i=0; i< color.size(); i++){
            cout<<color[i]+1;
            if(i!=color.size()-1) cout<<" ";
        }
    }

}

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