hdu 5305 Friends（2015多校第二场第6题）记忆化搜索

 1 #include <cstdio>
 2 #include <cstdlib>
 3 #include <cmath>
 4 #include <cstring>
 5 #include <iostream>
 6 #include <queue>
 7 #include <algorithm>
 8 #include <vector>
 9 using namespace std;
10 #define LL __int64
11 
12 int f[10],on[10],off[10];
13 int m,n;
14 struct node
15 {
16     int x,y;
17 }nn[30];
18 void init()
19 {
20     memset(f,0,sizeof(f));
21     memset(on,0,sizeof(on));
22     memset(off,0,sizeof(off));
23 }
24 int dfs(int cot)
25 {
26     int x,y,i,ans;
27     ans=0;
28     if(cot>=m)
29     {
30         for(i=1;i<=n;i++)
31         {
32             if(on[i]!=off[i])
33                 return 0;
34         }
35         return 1;
36     }
37     x=nn[cot].x;
38     y=nn[cot].y;
39     if(on[x]<f[x]/2&&on[y]<f[y]/2)
40     {
41         on[x]++;
42         on[y]++;
43         ans+=dfs(cot+1);
44         on[x]--;
45         on[y]--;
46     }
47     if(off[x]<f[x]/2&&off[y]<f[y]/2)
48     {
49         off[x]++;
50         off[y]++;
51         ans+=dfs(cot+1);
52         off[x]--;
53         off[y]--;
54     }
55     return ans;
56 }
57 
58 int main()
59 {
60     int i,T,ans;
61     while(~scanf("%d",&T))
62     {
63         while(T--)
64         {
65             scanf("%d%d",&n,&m);
66             init();
67             for(i=0;i<m;i++)
68             {
69                 scanf("%d%d",&nn[i].x,&nn[i].y);
70                 f[nn[i].x]++;
71                 f[nn[i].y]++;
72             }
73             if(m&1)
74             {
75                 printf("0\n");
76                 continue;
77             }
78             int flag=0;
79             for(i=1;i<=n;i++)
80             {
81                 if(f[i]&1)
82                 {
83                     flag=1;
84                     break;
85                 }
86             }
87             if(flag)
88             {
89                 printf("0\n");
90                 continue;
91             }
92             ans=dfs(0);
93             printf("%d\n",ans);
94         }
95     }
96     return 0;
97 }