10014 - Simple calculations
Time limit: 3.000 seconds
The Problem
There is a sequence of n+2 elements a0, a1,…, an+1 (n <= 3000; -1000 <= ai 1000). It is known that ai = (ai–1 + ai+1)/2 – ci for each i=1, 2, ..., n. You are given a0, an+1, c1, ... , cn. 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 an+1 each having two digits after decimal point, and the next n lines contain numbers ci (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 an+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
思路:
完整代码:
/*0.009s*/
#include<cstdio>
int main(void)
{
int t, n;
double a0, an, c, sum;
scanf("%d", &t);
while (t--)
{
sum = 0.0;
scanf("%d%lf%lf", &n, &a0, &an);
for (int i = 1; i <= n; i++)
{
scanf("%lf", &c);
sum += (n + 1 - i) * c;
}
printf("%.2f\n", (an + n * a0 - 2 * sum) / (n + 1));
if (t)
putchar('\n');
}
return 0;
}