暴力/DP Codeforces Beta Round #22 (Div. 2 Only) B. Bargaining Table

 1 /*
 2     题意：求最大矩形(全0)的面积
 3     暴力/dp：每对一个0查看它左下的最大矩形面积，更新ans
 4     注意：是字符串，没用空格，好事多磨，WA了多少次才发现:(
 5     详细解释：http://www.cnblogs.com/cszlg/p/3217478.html
 6 */
 7 #include <cstdio>
 8 #include <algorithm>
 9 #include <cstring>
10 #include <cmath>
11 using namespace std;
12 
13 const int MAXN = 33;
14 const int INF = 0x3f3f3f3f;
15 char s[MAXN][MAXN];
16 int n, m;
17 
18 int get_sum(int x, int y)
19 {
20     int res = 0;    int d, w = 30;
21     for (int i=x; i<n; ++i)
22     {
23         if (s[i][y] == ‘1‘)    break;
24         int j = y + 1;
25         while (j < m && s[i][j] == ‘0‘)    ++j;
26         d = i - x + 1;
27         if (w > j - y)    w = j - y;
28         res = max (res, (w + d) * 2);
29     }
30 
31     return res;
32 }
33 
34 int main(void)        //Codeforces Beta Round #22 (Div. 2 Only) B. Bargaining Table
35 {
36     while (scanf ("%d%d", &n, &m) == 2)
37     {
38         for (int i=0; i<n; ++i)
39         {
40             scanf ("%s", s[i]);
41         }
42 
43         int ans = 0;
44         for (int i=0; i<n; ++i)
45         {
46             for (int j=0; j<m; ++j)
47             {
48                 if (s[i][j] == ‘0‘)
49                 {
50                     ans = max (ans, get_sum (i, j));
51                 }
52             }
53         }
54 
55         printf ("%d\n", ans);
56     }
57 
58     return 0;
59 }