Kortit

#include <iostream>
#include <vector>
#include <algorithm>
#include <set>
 
using namespace std;
typedef long long LL;
 
// Always take smallest that beats the opponent. If does not exist, take smallest in hand.
 
void solve(){
    LL n; cin >> n;
    set<LL> have;
    for(LL i = 0; i < n/2; i++){
        LL x; cin >> x; have.insert(x);
    }
    set<LL> havenot;
    for(LL x = 1; x <= n; x++){
        if(have.count(x) == 0) havenot.insert(x);
    }
 
    LL ans = 0;
    for(LL r = 0; r < n/2; r++){
        LL x = *havenot.rbegin(); havenot.erase(x);
        auto yi = lower_bound(have.begin(), have.end(), x);
        if(yi == have.end()) have.erase(have.begin());
        else{
            have.erase(yi);
            ans++;
        }
    }
    cout << ans << "\n";
}
 
int main(){
    LL t; cin >> t; while(t--) solve();
}

Test 1

Group: 1, 2

Verdict: ACCEPTED

Test 2

Group: 2

Verdict: ACCEPTED