CSES – Building Teams

#include<bits/stdc++.h>
#define int long long
#define f first
#define s second
#define fastio ios_base::sync_with_stdio(0);cin.tie(0)
using namespace std;
//declare
const int maxn = 1e5+5;
int n,m,colors[maxn] = {0};
vector<int> G[maxn];
//
void dfs(int cur,int color){
    if(colors[cur]){
        if(colors[cur] != color){
            cout<<"IMPOSSIBLE\n";
            exit(0);
        }
        return;
    }
    colors[cur] = color;
    for(int adj : G[cur]){
        dfs(adj, 3-color);
    }
}
signed main(){
    fastio;
    cin>>n>>m;
    for(int i=0;i<m;i++){
        int a,b; cin>>a>>b;
        G[a].push_back(b);
        G[b].push_back(a);
    }
    for(int i=1;i<=n;i++){
        if(!colors[i]) dfs(i,1);
    }
    for(int i=1;i<=n;i++){
        cout<<colors[i]<<" ";
    }
    cout<<"\n";
    return 0;
}