poj 2018

#include<iostream>using namespace std;#define MAXN 100005int sum[MAXN];int f[MAXN];long long xmult(int i,int j,int k){ return (long long)(i-j)*(sum[k]-sum[j])-(long long)(k-j)*(sum[i]-sum[j]);}int queue[MAXN];int back;void run(int j){ while(back>=2&&xmult(j,queue[back-1],queue[back-2])<=0){ back--; } queue[back++]=j;}int main(){ int N,F; while(scanf("%d%d",&N,&F)!=EOF){ int i,j,k; for(i=1;i<=N;i++) scanf("%d",&f[i]); sum[0]=0; for(i=1;i<=N;i++) sum[i]=sum[i-1]+f[i]; long long res=-1; back=0; int p=0; for(i=F,j=0;i<=N;i++,j++){ run(j); if(back-1<p) p=back-1; while(p<back-1){ int x=queue[p]; int y=queue[p+1]; if(((long long)(sum[i]-sum[y])*1000/(i-y))>=((long long)(sum[i]-sum[x])*1000/(i-x))) p++; else break; } long long tmp; tmp=(long long)(sum[i]-sum[queue[p]])*1000/(i-queue[p]); if(tmp>res) res=tmp; } printf("%I64d/n",res); }}