UVa211 The Domino Effect (DFS)

链接：http://vjudge.net/problem/35575

分析：dfs暴力。

 1 #include <cstdio>
 2 #include <cstring>
 3
 4 const int r = 7;
 5 const int c = 8;
 6 const int m = 30;
 7 const int dir[2][2] = {
 8     {0, 1},
 9     {1, 0},
10 };
11
12 int map[r][c], id[r][r], checked[m], vis[r][c], ans;
13
14 void build() {
15     int num = 1;
16     for (int i = 0; i < r; i++)
17         for (int j = i; j < r; j++)
18             id[i][j] = id[j][i] = num++;
19 }
20
21 bool init() {
22     ans = 0;
23     memset(checked, 0, sizeof(checked));
24     memset(vis, 0, sizeof(vis));
25     for (int i = 0; i < r; i++)
26         for (int j = 0; j < c; j++)
27             if (scanf("%d", &map[i][j]) != 1) return false;
28     return true;
29 }
30
31 void print() {
32     for (int i = 0; i < r; i++) {
33         for (int j = 0; j < c; j++) printf("%4d", vis[i][j]);
34         printf("\n");
35     }
36     printf("\n");
37 }
38
39 void dfs(int x, int y, int cnt) {
40     if (cnt == 28) {
41         ans++;
42         print();
43         return;
44     }
45     if (y == c) { x++; y = 0; }
46
47     if (vis[x][y]) dfs(x, y + 1, cnt);
48     else {
49         for (int i = 0; i < 2; i++) {
50             int nx = x + dir[i][0], ny = y + dir[i][1];
51             if (nx >= r || ny >= c || vis[nx][ny]) continue;
52             int n = id[map[x][y]][map[nx][ny]];
53             if (checked[n]) continue;
54             vis[x][y] = vis[nx][ny] = n; checked[n] = 1;
55             dfs(x, y + 1, cnt + 1);
56             vis[x][y] = vis[nx][ny] = 0; checked[n] = 0;
57         }
58     }
59 }
60
61 int main() {
62     build();
63     int kase = 0;
64     while (init()) {
65         if (kase) printf("\n\n\n");
66         printf("Layout #%d:\n\n", ++kase);
67         for (int i = 0; i < r; i++) {
68             for (int j = 0; j < c; j++)
69                 printf("%4d", map[i][j]);
70             printf("\n");
71         }
72         printf("\nMaps resulting from layout #%d are:\n\n", kase);
73         dfs(0, 0, 0);
74         printf("There are %d solution(s) for layout #%d.\n", ans, kase);
75     }
76     return 0;
77 }