Codeforces 22B Bargaining Table

http://www.codeforces.com/problemset/problem/22/B

题意:求出n*m的方格图中全是0的矩阵的最大周长

思路:枚举

 #include<cstdio>
 #include<cmath>
 #include<algorithm>
 #include<cstring>
 #include<iostream>
 int n,m,a[][],h[][];
 char s[];
 int read(){
     int t=,f=;char ch=getchar();
     while (ch<''||ch>''){if (ch=='-') f=-;ch=getchar();}
     while (''<=ch&&ch<=''){t=t*+ch-'';ch=getchar();}
     return t*f;
 }
 int main(){
     n=read();m=read();
     for (int i=;i<=n;i++){
         scanf("%s",s+);
         for (int j=;j<=m;j++)
          a[i][j]=s[j]-'';
     }
     for (int i=;i<=n;i++)
      for (int j=;j<=m;j++){
         if (a[i][j]) continue;
         if (i!=&&a[i-][j]==) h[i][j]=h[i-][j]+;
         else h[i][j]=;
      }
     int ans=;
     for (int i=;i<=n;i++)
      for (int j=;j<=m;j++)
       if (a[i][j]==)
      {
         int ll=<<;
         for (int k=j;k>=&&a[i][k]==;k--){
             ll=std::min(ll,h[i][k]);
             ans=std::max(ans,ll+j-k+);
         }
      }
     printf("%d\n",ans*);
     return ;
 }