C :

#include<stdio.h>
int a[1000001];
main() {
	int j,i,n,m;
	scanf("%d %d",&n,&m);
	for(i = 0; i < n; i++) {
		scanf("%d",&a[i]);
	}
	double avg = 0;
	for(i = 0; i <= n - m; i++) {
		//求m个小时的最大值
		double s = 0;
		for(j = i; j < i + m ; j++) {
			s = s + a[j];
		}
		s = s / m;

		if(s > avg) {
			avg = s;
		}

	}

	printf("%.2f",avg);
}

C++ :

#include <bits/stdc++.h>
using namespace std;
int a[110];
int main(){
	int n,m;
	cin>>n>>m;
	for(int i=0;i<n;i++)
	{
		cin>>a[i];
	}
	float max=0;
	int s;
	for(int i=0;i<n-m+1;i++)
	{
		s=0;
		for(int j=i;j<m+i;j++)
		{
			s+=a[j];
		}
		if(s>max)
		{
			max=s;
		}
	}
	cout<<fixed<<setprecision(2)<<max/m<<endl;
	return 0;
}

Python :

n,m = map(int,input().split())
myList = list(map(int,input().split()))
max = 0
for i in range(0,n - m + 1):
     s = 0
     for j in range(i,i + m):
          s = s + myList[j]
     if s / m > max:
          max = s / m
print("%.2f"%(max))