这里是根据题解区中的dalao们逆推+优先队列的思路的完形填空

#include<bits/stdc++.h>
using namespace std;
#define rt register int
int n,k,hh,tt;
int e[100005],q[100005];
long long dp[100005],sum;
int main()
{
	scanf("%d%d",&n,&k);
	for(rt i=1;i<=n;++i)
		scanf("%d",&e[i]),sum+=e[i];	
	for(rt i=1;i<=n+1;++i)dp[i]=9999999999999999;
	hh=tt=1;
	for(rt i=1;i<=n+1;++i){
		while(q[hh]<i-k-1&&hh<=tt)hh++;
		dp[i]=min(dp[q[hh]]+e[i],dp[i]);
		while(dp[i]<dp[q[tt]]&&hh<=tt)tt--;
		q[++tt]=i;
	}
	printf("%lld\n",sum-dp[n+1]);
	return 0;
}