Uva 10014 Simple calculations

 Simple calculations 

The Problem

There is a sequence of n+2 elements a₀, a₁,…, a_n+1 (n <= 3000; -1000 <=  a_i 1000). It is known that a_i = (a_i–1 + a_i+1)/2 – c_i   for each i=1, 2, ..., n. You are given a₀, a_n+1, c₁, ... , c_n. Write a program which calculates a₁.

The Input

The first line is the number of test cases, followed by a blank line.

For each test case, the first line of an input file contains an integer n. The next two lines consist of numbers a₀ and a_n+1 each having two digits after decimal point, and the next n lines contain numbers c_i (also with two digits after decimal point), one number per line.

Each test case will be separated by a single line.

The Output

For each test case, the output file should contain a₁ in the same format as a₀ and a_n+1.

Print a blank line between the outputs for two consecutive test cases.

Sample Input

1

1
50.50
25.50
10.15

Sample Output

27.85

#include<stdio.h>
#include<string.h>

int main()
{
    int T, n, i;
    double first, final, sum, temp, ans;
    scanf("%d", &T);
    while(T--)
    {
        scanf("%d", &n);
        scanf("%lf", &first);
        scanf("%lf", &final);
        for(i=1,sum=0; i<=n; ++i)
        {
            scanf("%lf", &temp);
            sum += 2.0*(n+1-i)*temp;
        }
        
        ans = n*first+final-sum;
        printf("%.2lf\n", ans/(n+1));
        
        if(T != 0) printf("\n");
    }
    return 0;
}