[luoguP1169] [ZJOI2007]棋盘制作（单调栈）

 1 #include <cstdio>
 2 #include <iostream>
 3 
 4 using namespace std;
 5 
 6 const int MAXN = 2001;
 7 int n, m, ans1, ans2, top;
 8 int a[MAXN][MAXN][2], s[MAXN], r[MAXN], l[MAXN];
 9 
10 inline void work(int k)
11 {
12     int i, j;
13     for(i = 0; i <= 1; i++)
14     {
15         a[k][0][i] = a[k][m + 1][i] = -1;
16         top = 0;
17         for(j = 1; j <= m + 1; j++)
18         {
19             while(top && a[k][s[top]][i] > a[k][j][i]) r[s[top--]] = j;
20             s[++top] = j;
21         }
22         top = 0;
23         for(j = m; j >= 0; j--)
24         {
25             while(top && a[k][s[top]][i] > a[k][j][i]) l[s[top--]] = j;
26             s[++top] = j;
27         }
28         for(j = 1; j <= m; j++)
29         {
30             ans1 = max(ans1, min(a[k][j][i], r[j] - l[j] - 1) * min(a[k][j][i], r[j] - l[j] - 1));
31             ans2 = max(ans2, a[k][j][i] * (r[j] - l[j] - 1));
32         }
33     }
34 }
35 
36 int main()
37 {
38     int i, j, x;
39     scanf("%d %d", &n, &m);
40     for(i = 1; i <= n; i++)
41         for(j = 1; j <= m; j++)
42         {
43             scanf("%d", &x);
44             if((i + j) % 2) x ^= 1;
45             a[i][j][x] = a[i - 1][j][x] + 1;
46         }
47     for(i = 1; i <= n; i++) work(i);
48     printf("%d\n%d\n", ans1, ans2);
49     return 0;
50 }