codeforces - restore the permutation by merger

#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;
        ll ara[n*2+1],i;
        for(i=0;i<n*2;i++)cin>>ara[i];
        map<ll,ll>mp;
        for(i=0;i<n*2;i++)
        {
            if(mp[ara[i]]==0)cout<<ara[i]<<" ";
            mp[ara[i]]++;
        }
        cout<<endl;
    }
}