HAOI2007 修筑绿化带

 1 // luogu-judger-enable-o2
 2 #include <bits/stdc++.h>
 3 using namespace std;
 4 
 5 struct Monoque{
 6     int head,tail,q[2005],qt[2005];
 7     Monoque() {
 8         head=0;
 9         tail=-1;
10         memset(q,0,sizeof q);
11     }
12     void push(int val,int tim) {
13         while(q[tail]>=val && head<=tail) tail--;
14         q[++tail]=val;
15         qt[tail]=tim;
16     }
17     int front(int tim) {
18         if(head>tail) return 1e+5;
19         while(qt[head]<tim && head<=tail) head++;
20         if(head>tail) return 1e+5;
21         return q[head];
22     }
23 } p[2005],q[2005];
24 
25 int n,m,a,b,c,d,x[1005][1005],y[1005][1005],w[1005][1005],z[1005][1005],s[1005][1005],ans=0;
26 
27 int rect(int l1,int r1,int l2,int r2) {
28     l1--; r1--;
29     return s[l2][r2]-s[l1][r2]-s[l2][r1]+s[l1][r1];
30 }
31 
32 int main(){
33     ios::sync_with_stdio(false);
34     cin>>n>>m>>a>>b>>c>>d;
35     for(int i=1;i<=n;i++) 
36         for(int j=1;j<=m;j++)
37             cin>>x[i][j],
38             s[i][j]=s[i-1][j]+s[i][j-1]-s[i-1][j-1]+x[i][j];
39     for(int i=1;i<=n-a+1;i++)
40         for(int j=1;j<=m-b+1;j++)
41             x[i][j]=rect(i,j,i+a-1,j+b-1);
42     for(int i=1;i<=n-c+1;i++)
43         for(int j=1;j<=m-d+1;j++)
44             w[i][j]=rect(i,j,i+c-1,j+d-1);
45     // time : a-c  b-d
46     for(int i=1;i<=n-c+1;i++) {
47         for(int j=1;j<=m-d+1;j++) { 
48             z[i][j]=q[j].front(i);
49             q[j].push(p[i].front(j),i+a-c-1);
50             p[i].push(w[i][j],j+b-d-1);
51         }
52     }
53     for(int i=1;i<=n-a+1;i++) {
54         for(int j=1;j<=m-b+1;j++) {
55             //printf("i=%d j=%d  %d,%d  x=%d z=%d\n",i,j,i+a-c,j+b-d,x[i][j],z[i+a-c][j+b-d]);
56             ans=max(ans,x[i][j]-z[i+a-c][j+b-d]);
57         }
58     }
59     cout<<ans<<endl;
60 }