HackerEarth A XOR value problem solution

In this HackerEarth A XOR value problem solution You are given an array A consisting of N integer values. Find an integer K such that the value of the following function is minimized:

• Sigma(i=1,i=N) (A[i] XOR K), XOR represents a bitwise XOR operation

If multiple such K exist, then print the minimum possible value of K.

#include<bits/stdc++.h>
#define ll long long int
using namespace std;

void solve(){
    int n;
    cin >> n;
    assert(1 <= n and n <= 100000);

    ll a[n+1];
    for(int i = 1 ; i <= n ; i++)
    {
        cin >> a[i];
        assert((ll)1 <= a[i] and a[i] <= 1000000000000000000);
    }

    ll k = 0;
    for(int i = 0 ; i < 60 ; i++)
    {
        ll vl = (1LL << i);
        int cnt = 0;
        for(int j = 1 ; j <= n ; j++)
        {
            if(vl & a[j])
            {
                cnt++;
            }
        }

        int ncnt = n - cnt;

        if(cnt > ncnt)
        {
            k += vl;
        }
    }

    cout << k << endl;
}

int main(){
    int t;
    cin >> t;
    assert(1 <= t and t <= 10);
    while(t--){
        solve();
    }
}