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=0,f=1;char c=getchar();
    while (c<'0'||c>'9') {if (c=='-') f=-1;c=getchar();}
    while (c>='0'&&c<='9') x=(x<<1)+(x<<3)+(c^48),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
";
#else
    const char LL[]="%lld
";
#endif
    n=read(),m=read();
    for (int i=1;i<=n;i++) a[i]=a[i-1]+read();
    int head=1,tail=1;
    for (int i=1;i<=n+1;i++)
    {
        while (q[head]<i-m-1) head++;
        f[i]=f[q[head]]+a[i-1]-a[q[head]];
        while (head<=tail&&f[q[tail]]-a[q[tail]]<=f[i]-a[i]) tail--;
        q[++tail]=i;
    }
    cout<<f[n+1];
    return 0;
}