题解 | 牛牛的数学作业

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

const int N=1e5+10;

int t,n,a[N];

int main(){
	cin>>t;
	while(t--){
		cin>>n;
		int mi=1e5+10,ma=-1;
		long long sum=0;
		for(int i=1;i<=n;i++){
			scanf("%d",&a[i]);
			mi=min(mi,a[i]);
			ma=max(ma,a[i]);
			sum=sum+a[i];
		}
		int jc=ma-mi;
		double avg=sum*1.0/n,fc=0;
		for(int i=1;i<=n;i++){
			fc=fc+(a[i]-avg)*(a[i]-avg)/n*1.0;
		}
		cout<<jc<<" "<<fixed<<setprecision(3)<<fc<<endl;
	}

    return 0;
}