牛客网多校训练第一场 D - Two Graphs

链接：

https://www.nowcoder.com/acm/contest/139/D

题意：

两个无向简单图都有n（1≤n≤8）个顶点，图G1有m1条边，图G2有m2条边，问G2有多少个子图与G1同构。

分析：

枚举所有的映射方案，再判断合法性，把每一合法映射所用到的边状态压缩一下，装到集合里去重即可。

代码：

 1 import java.io.*;
 2 import java.util.*;
 3 
 4 public class Main {
 5     Scanner cin = new Scanner(new BufferedInputStream(System.in));
 6     final int UP = 8 + 5;
 7     int n, map[] = new int[99], cor[] = new int[UP];
 8     boolean G[][] = new boolean[UP][UP], G2[][] = new boolean[UP][UP];
 9     boolean opt[] = new boolean[UP];
10     HashSet<Integer> set = new HashSet<Integer>();
11     
12     void init() {
13         for(int r = 0; r < UP; r++)
14             for(int c = 0; c < UP; c++) G[r][c] = G2[r][c] = false;
15     }
16     
17     void dfs(int d) {
18         if(d == n + 1) {
19             int code = 0;
20             for(int f = 1; f <= 8; f++) {
21                 for(int b = 1; b <= 8; b++) {
22                     if(!G[f][b]) continue;
23                     if(!G2[cor[f]][cor[b]]) return;
24                     code |= 1 << map[cor[f]*10+cor[b]];
25                 }
26             }
27             set.add(code);
28             return;
29         }
30         for(int i = 1; i <= n; i++) {
31             if(opt[i]) continue;
32             opt[i] = true;
33             cor[d] = i;
34             dfs(d+1);
35             opt[i] = false;
36         }
37     }
38     
39     void MAIN() {
40         while(cin.hasNext()) {
41             init();
42             n = cin.nextInt();
43             int m = cin.nextInt();
44             int m2 = cin.nextInt();
45             for(int f, b, i = 0; i < m; i++) {
46                 f = cin.nextInt();
47                 b = cin.nextInt();
48                 G[f][b] = G[b][f] = true;
49             }
50             for(int f, b, i = 0; i < m2; i++) {
51                 f = cin.nextInt();
52                 b = cin.nextInt();
53                 G2[f][b] = G2[b][f] = true;
54                 map[f*10+b] = map[b*10+f] = i;
55             }
56             
57             set.clear();
58             dfs(1);
59             System.out.println(set.size());
60         }
61     }
62     
63     public static void main(String args[]) { new Main().MAIN(); }
64 }