UVA 10014 Simple calculations

UVA-10014

/*************************************************************************
> File Name: UVA-10014.cpp
> Author: Narsh
>
> Created Time: 2016年07月15日 星期五 10时51分40秒
************************************************************************/

#include <iostream>
#include <algorithm>
#include <cstdio>
#include <cstring>
#include <cmath>
using namespace std;
int n,t;
double a[3100],c[3100],sum;
int main () {
scanf("%d",&t);
while (t--) {
scanf("%d",&n);
scanf("%lf%lf",&a[0],&a[n+1]);
sum = a[0]*n+a[n+1];
for (int i = 1; i <= n; i++) {
scanf("%lf",&c[i]);
sum-=c[i]*(n-i+1)*2.0;
}
sum= sum/ (1.0*n+1);
printf("%.2lf\n",sum);
if (t) printf("\n");
}
}