CF 22B. Bargaining Table

水题。好久没有写过优化搜索题了。

#include <cstdio>
#include <cstring>
#include <iostream>
#include <vector>
using namespace std;
char str[31][31];
int r[31][31];
int c[31][31];
int judge(int rx,int ry,int lx,int ly)
{
    int i,j;
    for(i = lx;i <= rx;i ++)
    {
        for(j = ly;j <= ry;j ++)
        {
            if(str[i-1][j-1] == '1')
            return 0;
        }
    }
    return 1;
}
int main()
{
    int n,m,i,j,k,u,ans;
    scanf("%d%d",&n,&m);
    for(i = 0;i < n;i ++)
    scanf("%s",str[i]);
    ans = 0;
    for(i = 1;i <= n;i ++)
    {
        for(j = 1;j <= m;j ++)
        {
           if(str[i-1][j-1] == '0')
           {
               r[i][j] = r[i-1][j] + 1;
               c[i][j] = c[i][j-1] + 1;
           }
           else
           {
               r[i][j] = 0;
               c[i][j] = 0;
           }
        }
    }
    for(i = n;i >= 1;i --)
    {
        for(j = m;j >= 1;j --)
        {
            for(k = 1;k <= r[i][j];k ++)
            {
                for(u = 1;u <= c[i][j];u ++)
                {
                    if(ans >= (k+u)*2) continue;
                    if(judge(i,j,i-k+1,j-u+1))
                    {
                        ans = max(ans,(k+u)*2);
                    }
                }
            }
        }
    }
    printf("%d
",ans);
    return 0;
}