hihoCoder#1048 状态压缩·二

 1 #include <iostream>
 2 #include <cstring>
 3 
 4 using namespace std;
 5 
 6 #define MAX_N 1024
 7 #define MAX_M 8
 8 #define MAX_S 4096
 9 #define MOD 1000000007
10 
11 int f[MAX_N][MAX_M][MAX_S];
12 int N, M;
13 
14 bool freep(int s, int o) {
15   return !(s & (1 << o));
16 }
17 
18 int mark(int s, int o) {
19   return s |= (1 << o);
20 }
21 
22 int mark(int s, int o1, int o2) {
23   return mark(s, o1) | mark(s, o2);
24 }
25 
26 int main() {
27   cin >> N >> M;
28   memset(f, 0, sizeof(f));
29 
30   for (int i = 1; i <= N; i++) {
31     for (int s = 0; s < (1 << (2 * M + 1)); s++)
32       f[i][M + 1][s] = 1;
33   }
34   for (int j = 1; j <= M; j++) {
35     for (int s = 0; s < (1 << (2 * M + 1)); s++)
36       f[N + 1][j][s] = 1;
37   }
38 
39   for (int i = N; i >= 1; i--) {
40     for (int j = M; j >= 1; j--) {
41       for (int k = (1 << (2 * M)) - 1; k >= 0; k--) {
42         int s = k << 1;
43         // pass
44         if (!freep(s, j)) {
45           if (j < M)
46             f[i][j][s] = f[i][j + 1][s];
47           if (j == M)
48             f[i][j][s] = f[i + 1][1][(s >> M) >> 1 << 1];
49         }
50         if (freep(s, j)) {
51           // impossible
52           if ((j == M || !freep(s, j + 1)) && (i == N || !freep(s, j + M)))
53             f[i][j][s] = 0;
54           // right
55           if (j < M && freep(s, j + 1) && (i == N || !freep(s, j + M)))
56             f[i][j][s] += f[i][j][mark(s, j, j + 1)];
57           // down
58           if (i < N && freep(s, j + M) && (j == M || !freep(s, j + 1)))
59             f[i][j][s] += f[i][j][mark(s, j, j + M)];
60           // right & down
61           if (j < M && freep(s, j + 1) && i < N && freep(s, j + M))
62             f[i][j][s] = (f[i][j][mark(s, j, j + 1)] + f[i][j][mark(s, j, j + M)]) % MOD;
63         }
64       }
65     }
66   }
67 
68   cout << f[1][1][0] << endl;
69 
70   return 0;
71 }