题解

#include<bits/stdc++.h>
#define sing using
#define dance namespace
#define rap std
#define basketball int
#define ikun double
sing dance rap;
basketball a[1001],n;
ikun sum;
basketball main() {
cin>>n;
for(basketball i=1;i<=n;i++) cin>>a[i];
sort(a+1,a+n+1);
for(basketball i=1;i<=n;i++) sum+=(n-i)a[i];
printf("%.2f",(ikun)sum/n1.0);
return 0;
}