题解

#include <bits/stdc++.h>
using namespace std;
const int N=1000001;
int n;
struct ds{
	double t;
	int id;
}a[N];
bool cmp(ds aa,ds bb)
{
	return aa.t<bb.t;
}
int main()
{
	cin>>n;
	for(int i=1;i<=n;++i)
	{
		cin>>a[i].t;
		a[i].id = i;
	} 
	sort(a+1,a+1+n,cmp);
	for(int i=1;i<=n;++i)
	{
		cout<<a[i].id<<" ";
	}
	cout<<endl;
	double sum1=0,sum2=0;
	for(int i=1;i<=n-1;++i)
	{
		sum1=sum1+a[i].t;
		sum2=sum2+sum1;
	} 
	printf("%.2f",sum2/n);
	return 0;
}