Codeforces 22B Bargaining Table

 1 #include<cstdio>
 2 #include<cmath>
 3 #include<algorithm>
 4 #include<cstring>
 5 #include<iostream>
 6 int n,m,a[50][50],h[50][50];
 7 char s[500];
 8 int read(){
 9     int t=0,f=1;char ch=getchar();
10     while (ch<‘0‘||ch>‘9‘){if (ch==‘-‘) f=-1;ch=getchar();}
11     while (‘0‘<=ch&&ch<=‘9‘){t=t*10+ch-‘0‘;ch=getchar();}
12     return t*f;
13 }
14 int main(){
15     n=read();m=read();
16     for (int i=1;i<=n;i++){
17         scanf("%s",s+1);
18         for (int j=1;j<=m;j++)
19          a[i][j]=s[j]-‘0‘;
20     }
21     for (int i=1;i<=n;i++)
22      for (int j=1;j<=m;j++){
23         if (a[i][j]) continue;
24         if (i!=1&&a[i-1][j]==0) h[i][j]=h[i-1][j]+1;
25         else h[i][j]=1;
26      }
27     int ans=0; 
28     for (int i=1;i<=n;i++)
29      for (int j=1;j<=m;j++)
30       if (a[i][j]==0)
31      {
32         int ll=1<<29;
33         for (int k=j;k>=1&&a[i][k]==0;k--){
34             ll=std::min(ll,h[i][k]);
35             ans=std::max(ans,ll+j-k+1);
36         }
37      }
38     printf("%d\n",ans*2); 
39     return 0;
40 }