BZOJ2442 Usaco2011 Open修剪草坪（动态规划+单调队列）

　　显然可以dp。显然可以单调队列优化一下。

#include<iostream>
#include<cstdio>
#include<cmath>
#include<cstdlib>
#include<cstring>
#include<algorithm>
using namespace std;
int read()
{
    int x=,f=;char c=getchar();
    while (c<''||c>'') {if (c=='-') f=-;c=getchar();}
    while (c>=''&&c<='') x=(x<<)+(x<<)+(c^),c=getchar();
    return x*f;
}
#define N 100010
int n,m,q[N];
long long a[N],f[N];
int main()
{
#ifndef ONLINE_JUDGE
    freopen("bzoj2442.in","r",stdin);
    freopen("bzoj2442.out","w",stdout);
    const char LL[]="%I64d\n";
#else
    const char LL[]="%lld\n";
#endif
    n=read(),m=read();
    for (int i=;i<=n;i++) a[i]=a[i-]+read();
    int head=,tail=;
    for (int i=;i<=n+;i++)
    {
        while (q[head]<i-m-) head++;
        f[i]=f[q[head]]+a[i-]-a[q[head]];
        while (head<=tail&&f[q[tail]]-a[q[tail]]<=f[i]-a[i]) tail--;
        q[++tail]=i;
    }
    cout<<f[n+];
    return ;
}