BZOJ 1177 Oil(特技枚举)

#include<set>
#include<map>
#include<ctime>
#include<queue>
#include<cmath>
#include<cstdio>
#include<vector>
#include<cstring>
#include<cstdlib>
#include<iostream>
#include<algorithm>
#define inf 100000000000000LL
#define pa pair<int,int>
#define ll long long
#define N 2505
#define fp(a,b,c) for(int a=b;a<=c;a++)
#define fd(a,b,c) for(int a=c;a>=b;a--)
using namespace std;
int n,m,K,ans;
int a[N][N],b[N][N],c[N][N],d[N][N],s[N][N];
int main()
{
    scanf("%d%d%d",&n,&m,&K);
    fp(i,1,n)fp(j,1,m)
    {
        int x;scanf("%d",&x);
        s[i][j]=s[i-1][j]+s[i][j-1]-s[i-1][j-1]+x;
    }
    fd(i,K,n)fd(j,K,m)s[i][j]-=s[i-K][j]+s[i][j-K]-s[i-K][j-K];

    fp(i,K,n)fp(j,K,m)a[i][j]=max(s[i][j],max(a[i-1][j],a[i][j-1]));
    fp(i,K,n)fd(j,K,m)b[i][j]=max(s[i][j],max(b[i-1][j],b[i][j+1]));
    fd(i,K,n)fp(j,K,m)c[i][j]=max(s[i][j],max(c[i+1][j],c[i][j-1]));
    fd(i,K,n)fd(j,K,m)d[i][j]=max(s[i][j],max(d[i+1][j],d[i][j+1]));

    fp(i,K,n-K)fp(j,K,m-K)ans=max(ans,a[i][j]+b[i][j+K]+c[i+K][m]);
    fp(i,K,n-K)fp(j,K+K,m)ans=max(ans,b[i][j]+d[i+K][j]+a[n][j-K]);
    fp(i,K+K,n)fp(j,K,m-K)ans=max(ans,c[i][j]+d[i][j+K]+a[i-K][m]);
    fp(i,K,n-K)fp(j,K,m-K)ans=max(ans,a[i][j]+c[i+K][j]+b[n][j+K]);

    fp(i,K,n)fp(j,K+K,m-K)ans=max(ans,s[i][j]+a[n][j-K]+b[n][j+K]);
    fp(i,K+K,n-K)fp(j,K,m)ans=max(ans,s[i][j]+a[i-K][m]+c[i+K][m]);

    printf("%d\n",ans);
    return 0;
}