bzoj1057: [ZJOI2007]棋盘制作--最大子矩阵

 1 #include<stdio.h>
 2 #include<string.h>
 3 #include<algorithm>
 4 #define maxn 2005
 5 using namespace std;
 6 int n,m,map[maxn][maxn],ans1,ans2,l[maxn],r[maxn],d[maxn],t;
 7 
 8 int main(){
 9     scanf("%d%d", &n, &m);
10     for (int i=1; i<=n; i++)
11         for (int j=1; j<=m; j++){
12             scanf("%d", &map[i][j]);
13             if ((i+j)&1) map[i][j]^=1;
14         }
15     for (int i=1; i<=n; i++){  //黑为奇数行列 
16         for (int j=1; j<=m; j++){
17             l[j]=r[j]=j;
18             if (map[i][j]) d[j]++;
19             else d[j]=0;
20         }
21         for (int j=1; j<=m; j++) if (d[j]) while (d[l[j]-1]>=d[j]) l[j]=l[l[j]-1];
22         for (int j=m; j>=1; j--) if (d[j]) while (d[r[j]+1]>=d[j]) r[j]=r[r[j]+1];
23         for (int j=1; j<=m; j++){
24             t=min(d[j],r[j]-l[j]+1);
25             ans1=max(ans1,t*t);
26             ans2=max(ans2,d[j]*(r[j]-l[j]+1));
27         }
28     }
29     memset(d,0,sizeof(d));
30     for (int i=1; i<=n; i++){  //白为奇数行列 
31         for (int j=1; j<=m; j++){
32             l[j]=r[j]=j;
33             if (!map[i][j]) d[j]++;
34             else d[j]=0;
35         }
36         for (int j=1; j<=m; j++) if (d[j]) while (d[l[j]-1]>=d[j]) l[j]=l[l[j]-1];
37         for (int j=m; j>=1; j--) if (d[j]) while (d[r[j]+1]>=d[j]) r[j]=r[r[j]+1];
38         for (int j=1; j<=m; j++){
39             t=min(d[j],r[j]-l[j]+1);
40             ans1=max(ans1,t*t);
41             ans2=max(ans2,d[j]*(r[j]-l[j]+1));
42         }
43     }
44     printf("%d\n%d\n", ans1, ans2);
45     return 0;
46 }