1 #include<stdio.h>
2 #include<string.h>
3 int n,m,min,father[15],map[15][15];
4 int find(int i)
5 {
6 if (father[i]!=i) return(find(father[i]));
7 return(father[i]);
8 }
9 void dfs(int now,int need)
10 {
11 int i,j,judge;
12 if (need>=min) return;
13 if (now==n)
14 {
15 if (need<min) min=need;
16 return;
17 }
18 for (i=0;i<now;i++)
19 {
20 judge=1;
21 for (j=0;j<now;j++)
22 if (find(j)==find(i)&&map[now][j]==0) judge=0;
23 if (judge==1){
24 father[now]=find(i);
25 dfs(now+1,need);
26 }
27 }
28 father[now]=now;
29 dfs(now+1,need+1);
30 return;
31 }
32 int main()
33 {
34 int i,j,k;
35 while (~scanf("%d%d",&n,&m))
36 {
37 memset(map,0,sizeof(map));
38 for (i=0;i<n;i++)
39 {
40 father[i]=i;
41 scanf("%d",&k);
42 while (k--)
43 {
44 scanf("%d",&j);
45 map[i][j]=map[j][i]=1;
46 }
47 }
48 min=m+1;
49 dfs(1,1);
50 if (min<=m) printf("%YES\n");
51 else printf("NO\n");
52 }
53 return 0;
54 }
http://acm.hdu.edu.cn/showproblem.php?pid=2208
