题解 | 牛牛的数学作业

#include<bits/stdc++.h>
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>arr(n);
        for(int i=0;i<n;i++){
            cin>>arr[i];
        }
        long long max_val= *max_element(arr.begin(),arr.end());
        long long min_val= *min_element(arr.begin(),arr.end());
        long long range=max_val-min_val;
        long long sum=0;
        for(long long num : arr){
            sum+=num;
        }
        long double averg=static_cast<double>(sum)/n;
        long double variance=0.0;
        for(long long num : arr){
            long double diff=num-averg;
            variance+=diff*diff;
        }
        variance/=n;
        cout<<range<<" "<<fixed<<setprecision(3)<<variance<<endl;
    }
    return 0;
}