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

struct node  
{
 	int t, id;  
} a[1010];

bool cmp(node x,node y)
{
 	return x.t < y.t;    
}

int n, i, j;
double ans;

int main()
{
 	cin >> n;    
 	for (i = 1; i <= n; i++)   
  	{
   		cin >> a[i].t;
   		a[i].id = i;             
  	} 
 	sort(a + 1, a + n + 1, cmp);
  	for (i = 1; i <= n; i++) cout << a[i].id << " "; 
  	cout << endl;
  	for (j = n - 1; j >= 1; j--)
  	{
   		i = n - j;
   		ans += a[i].t * j;                 
  	}
	cout << fixed << setprecision(2) << ans / n << endl;
  	return 0; 
}

发个题解

#include<bits/stdc++.h>
using namespace std;
int n;
double sum=0;
struct peo{
	int num;
	int t;
}m[164017];
bool cmp(peo a,peo b){
	return a.t<b.t;
}
int main(){
	cin>>n;
	for(int i=1;i<=n;i++){
		m[i].num=i;
		cin>>m[i].t;
	}
	sort(m+1,m+n+1,cmp);
	for(int i=1;i<=n;i++){
		cout<<m[i].num<<' ';
	}
	cout<<'\n';
	for(int i=n-1;i>=1;i--){
		sum+=m[n-i].t*i;
	}
	sum/=n;
	cout<<fixed<<setprecision(2)<<sum;
	return 0;
}