代码贴上

#include<iostream>
#include<algorithm>
#include<cstdio>
using namespace std;
struct intt
{
	int xh,m;
}a[100001];
bool cmp(intt a,intt b)
{
	if(a.m==b.m)
	  return a.xh<b.xh;
	return a.m<b.m;
}
int n,ans,k,kk;
int main()
{
	cin>>n;
	for(int i=1;i<=n;i++)
	{
	    scanf("%d",&a[i].m);
	    a[i].xh=i;
	}
	sort(a+1,a+1+n,cmp);
	for(int i=1;i<=n;i++)
	  cout<<a[i].xh<<" ";
	cout<<"\n";
	for(int i=n-1;i>=1;i--)
    {
        k=n-i;
        ans+=a[i].m*k;               
    }
    printf("%.2lf",double(ans*1.0/n));
}

检查不出来QAQ