codeforces - gcd compression

#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define fast ios_base::sync_with_stdio(0),cin.tie(NULL)
int main()
{
    fast;
    ll t;
    cin>>t;
    while(t--)
    {
        ll n;
        cin>>n;
        vector<ll>odd,even;
        ll i,cnt=0;
        for(i=0;i<n*2;i++)
        {
            ll x;
            cin>>x;
            if(x%2)odd.push_back(i+1);
            else even.push_back(i+1);
        }
        //sort(odd.begin(),odd.end());
        //sort(even.begin(),even.end());
        if(odd.size()>=2)for(i=0;i<odd.size()-1 && cnt<n-1;i+=2)
        {
            cout<<odd[i] <<" "<<odd[i+1]<<endl;
            cnt++;
        }
        if(even.size()>=2)for(i=0;i<even.size()-1&& cnt<n-1;i+=2)
        {
            cout<<even[i] <<" "<<even[i+1]<<endl;
            cnt++;
        }
    }
}