Sum this up Problem Code EVOFWEIRDSUM

#include<bits/stdc++.h>
using namespace std;

typedef long long ll;

const int mod = 1e9 + 7;
const int N = 2e6 + 10;

typedef pair<int, int> PII;
typedef long long ll;
int n, k;
int a[N];

void solve() {
    cin >> n;
    ll ans = 0;
    vector<int> a(n);
    for (int i = 0; i < n; i ++) {
        cin >> a[i];
    }
    sort(a.begin(), a.end());

    for (int i = 0;  i < n; i ++) {
        ans += a[i];
    }
    cout << ans  / n<< endl;
}
int main(){
    int t;
    cin >>t;
    
    while (t --) solve();
    return 0;
}

https://discuss.codechef.com/t/evofweirdsum-editorial/97058 化简公式 S(c) = 1(c[1] + c[n]) / 2; E(s(c)) = (E(c[1] + c[n])) / 2; 线性期望性质 E(S(c)) = (E(c[1]) + E(c[n])) / 2 = (AVG(A) + AVG(A)) / 2 = AVG(A);