题解 | #随机序列#

#include<bits/stdc++.h>
 using namespace std;
  const int N=1e6+10;
  int a[N];
   int main ()
    {
     int t,n;
      cin>>t;
    while (t--){
    cin>>n;
    double sum=0,ans=0;
    
   for (int i=0;i<n;i++)
     scanf("%d",&a[i]),sum+=a[i];
    sort(a,a+n);
    sum/=n;
    for (int i=0;i<n;i++){
        ans+=pow(a[i]-sum,2);
        
        }
        ans/=n;
    printf("%d %.3lf\n",a[n-1]-a[0],ans);
    
        }
        return 0;

    }