poj 2018 Best Cow Fences

#include <iostream>
#include <cstdio>
#include <cstring>

using namespace std;

long long f[100100];
int q[100100];

int main()
{
    int n,F,a;
    while(scanf("%d%d",&n,&F)==2)
    {
        for(int i=1;i<=n;i++)
        {
            scanf("%d",&a);
            f[i]=f[i-1]+a;
        }

        int l=0,r=0;
        long long ans=0;
        for(int i=F;i<=n;i++)
        {
            while(l+1<r&&(f[i-F]-f[q[r-1]])*(q[r-1]-q[r-2])<=(f[q[r-1]]-f[q[r-2]])*(i-F-q[r-1])) r--;
            q[r++]=i-F;
            while(l+1<r&&(f[i]-f[q[l+1]])*(i-q[l])>=(f[i]-f[q[l]])*(i-q[l+1])) l++;
            ans=max(ans,(f[i]-f[q[l]])*1000/(i-q[l]));
        }
        printf("%lld\n",ans);
    }
    return 0;
}