1806B - Mex Master - CodeForces Solution

#include <bits/stdc++.h>
using namespace std;
#define int long long
#define INF (int)1e18
#define f first
#define s second

mt19937_64 RNG(chrono::steady_clock::now().time_since_epoch().count());

void Solve() 
{
    int n; cin>>n;
    vector <int> a(n);
    int cnt = 0;
    int cnt1 = 0;
    for (int i=0; i<n; i++){
        cin>>a[i];
        
        if (a[i] == 0)
        cnt++;
        
        if (a[i]== 1){
            cnt1++;
        }
    }
    
    if (cnt <= (n + 1)/2){
        cout<<0<<"\n";
        return;
    }
    
    if (cnt + cnt1 == n && cnt != n){
        cout<<2<<"\n";
    } else {
        cout<<1<<"\n";
    }
}

int32_t main() 
{
    auto begin = std::chrono::high_resolution_clock::now();
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    int t = 1;
    cin >> t;
    for(int i = 1; i <= t; i++) 
    {
        //cout << "Case #" << i << ": ";
        Solve();
    }
    auto end = std::chrono::high_resolution_clock::now();
    auto elapsed = std::chrono::duration_cast<std::chrono::nanoseconds>(end - begin);
    cerr << "Time measured: " << elapsed.count() * 1e-9 << " seconds.\n"; 
    return 0;
}