题解

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

int water[1001];
int main(){
    int n,cnt=0;
    cin >> n;
	for (int i=1;i<=n;i++){
        cin >> water[i];
    }
    sort(water+1,water+1+n);
    for (int i=1;i<=n;i++){
        cnt+=water[i]*(n-i);
    }
    double average=cnt*1.0/n;
    printf("%.2lf",average);
}