前面都对，后面平均数错了：

#include<iostream>
#include<iomanip>
using namespace std;
int n;
double sum=0;
struct node
{
    int num,t;
} a[1005];
int main()
{
    cin>>n;
    for (int i=1;i<=n;i++)
    {
        a[i].num=i;
        cin>>a[i].t;
    }
    for (int i=1;i<=n-1;i++)
    {
        for (int j=i+1;j<=n;j++)
        {
            if (a[i].t>a[j].t)
            {
                swap(a[i].t,a[j].t);
                swap(a[i].num,a[j].num);
            }
        }
    }
    for (int i=1;i<=n;i++)
    {
        sum+=double(a[i].t*(n-i));
    }
    for (int i=1;i<=n;i++)
    {
        cout<<a[i].num<<" ";
    }
    cout<<endl;
    cout<<setprecision(2)<<sum/double(n)<<endl;
    return 0;
}