On the usage of a magic function

Title Description

Given a length of n Sequence a_i, Definition a[i] For the first time i The value of two elements . Now we need to find the most valuable in the sequence “ The paragraph ”. A paragraph is defined as having a length of [S,T] A continuous sequence between . The most valuable paragraph refers to the paragraph with the highest average value ,

Average of paragraphs = Total paragraph value / Paragraph length .

I / O format

Input format ：

The first line is an integer n, Represents sequence length .

The second line is two integers S and T, Indicates the range of paragraph length , stay [S,T] Between .

Third line to third line n+2 That's ok , An integer in each line represents the value index of each element .

Output format ：

A real number , Retain 3 Decimal place , Represents the average value of the best paragraph .

I/o sample

sample input #1：

3

2 2

3

-1

2

sample output #1：

1.000

explain

【 Data range 】

about 30% Data are available. n<=1000.

about 100% Data are available. n<=100000,1<=S<=T<=n,-10000<= Value index <=10000.

---

#include <iostream>
#include <cstring>
#include <algorithm>
using namespace std;
const int N = 1e5+10;
int n,s,t;
int a[N];
double res;
int main()
{
    scanf("%d", &n);
    scanf("%d%d", &s, &t);
    for(int i=1;i<=n;i++) scanf("%d", &a[i]);
    
    for(int i=1;i<=n;i++) a[i]+=a[i-1];
    
    for(int i=s;i<=t&&(double)clock() / CLOCKS_PER_SEC <= 0.95;i++)
    {
        for(int j=1;j+i-1<=n;j++)
        {
            int r = j+i-1;
            double sum = a[r] - a[j-1];
            res = max(res, (double)(sum*1.0/i));
        }
    }
    printf("%.3lf",res);
    return 0;
}

The following code can ensure the cycle 0.95s after Automatically exit the loop ...

(double)clock() / CLOCKS_PER_SEC <= 0.95