[HAOI2007]修筑绿化带

传送门：

#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <algorithm>
#include <iostream>
#include <vector>
using namespace std;
#define ll long long
#define re register
#define pb push_back
const int N=1005;
inline void read(int &a)
{
    a=0;
    int d=1;
    char ch;
    while(ch=getchar(),ch>'9'||ch<'0')
        if(ch=='-')
            d=-1;
    a=ch^48;
    while(ch=getchar(),ch>='0'&&ch<='9')
        a=(a<<3)+(a<<1)+(ch^48);
    a*=d;
}
int a[N][N],minq1[N][N],minq2[N][N],q[N],x[N][N],y[N][N];
int main()
{
    int n,m,A,B,C,D,h1,h2,t1,t2;
    read(n);
    read(m);
    read(A);
    read(B);
    read(C);
    read(D);
    for(re int i=1;i<=n;i++)
        for(re int j=1;j<=m;j++)
        {
            read(a[i][j]);
            a[i][j]+=a[i-1][j]+a[i][j-1]-a[i-1][j-1];
        }
    for(re int i=C+1;i<n;i++)
        for(re int j=D+1;j<m;j++)
            y[i][j]=a[i][j]-a[i-C][j]-a[i][j-D]+a[i-C][j-D];
    for(re int i=A;i<=n;i++)
        for(re int j=B;j<=m;j++)
            x[i][j]=a[i][j]-a[i-A][j]-a[i][j-B]+a[i-A][j-B];
    for(re int i=C+1;i<n;i++)
    {
        t1=h1=1;
        for(re int j=D+1;j<m;j++)
        {
            while(h1<t1&&j-q[h1]>=B-2-D)
                h1++;
            while(h1<t1&&y[i][q[t1-1]]>=y[i][j])
                t1--;
            q[t1++]=j;
            if(j+1>=B)
                minq1[i][j+1]=y[i][q[h1]];
        }
    }
    for(re int i=B;i<=m;i++)
    {
        t1=h1=1;
        for(re int j=C+1;j<n;j++)
        {
            while(h1<t1&&j-q[h1]>=A-2-C)
                h1++;
            while(h1<t1&&minq1[q[t1-1]][i]>=minq1[j][i])
                t1--;
            q[t1++]=j;
            if(j+1>=A)
                minq2[j+1][i]=minq1[q[h1]][i];
        }
    }
    int ans=0;
    for(re int i=A;i<=n;i++)
        for(re int j=B;j<=m;j++)
            ans=max(ans,x[i][j]-minq2[i][j]);
    printf("%d",ans);
    return 0;
}