题解 | 牛牛的数学作业

#include<iostream>
#include<cmath>
#include<algorithm>
#include<vector>
#include<iomanip>
using namespace std;
int main(){
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    int t;
    cin >> t;
    while(t--){
        int n;
        cin >> n;
        vector<long long>b(n);
        long long sum=0;
        for(int j=0;j<n;j++){
            cin >> b[j];
            sum+=b[j];
        }
        sort(b.begin(),b.end());
        long long range=b.back()-b[0];
        double avg=(double)sum/n;
        double variance=0.0;
        for(int j=0;j<n;j++){
            double diff=b[j]-avg;
            variance+=diff*diff;
        }
        variance/=n;
        cout << range<<' '<<fixed<<setprecision(3)<<variance<<endl;
    }
    return 0;
}