Submission #75822405

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Source Code Expand

#pragma GCC optimize("O3,unroll-loops")
#include <bits/stdc++.h>
#define int long long
#define double long double
using namespace std;

array<double, 101010> M, sum;
double mid, ans;
int N;

signed main() {
	cin.tie(0)->sync_with_stdio(0);
	cout.precision(15);

	cin >> N;

	for (int i = 1; i <= N; i++) {
		sum[i] = sum[i - 1] + i;
	}

	for (int i = 0; i < N; i++) {
		cin >> M[i];
	}
	sort(M.begin(), M.begin() + N);

	for (double i = 1; i <= N; i++) {
		mid += (i * sum[N - i + 1] - (N - i + 1) * (i - 1)) / (N - i + 1);
	}

	mid /= N;

	double cur = mid + (double)(N - 1) / 4;

	for (int i = 0; i < N; i++, cur -= 0.5) {
		ans += cur * M[i];
	}

	cout << fixed << ans << '\n';

	return 0;
}

Submission Info

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