hdu 5305 Friends(dfs)

Problem Description

There are

offline friends too, but different people can have different number of online or offline friends). Please determine how many ways there are to satisfy their requirements.

Input

The first line of the input is a single integer

and every friend relationship will appear at most once.

Output

For each testcase, print one number indicating the answer.

Sample Input

3 3

1 2

2 3

3 1

4 4

1 2

2 3

3 4

4 1

Sample Output

 1 #include<cstdio>
 2 #include<cstring>
 3 #include<algorithm>
 4 #include<cmath>
 5 using namespace std;
 6 int ans,n,m;
 7 int v[10],v1[10],v2[10];
 8 struct p
 9 {
10    int u,v;
11 };p s[60];
12 void dfs(int i)
13 {
14      if (i==m+1)
15      {
16          ans++;
17          return ;
18      }
19      if (v1[s[i].u]&&v1[s[i].v])
20      {
21           v1[s[i].u]--;
22           v1[s[i].v]--;
23           dfs(i+1);
24           v1[s[i].u]++;
25           v1[s[i].v]++;
26      }
27      if (v2[s[i].u]&&v2[s[i].v])
28      {
29           v2[s[i].u]--;
30           v2[s[i].v]--;
31           dfs(i+1);
32           v2[s[i].u]++;
33           v2[s[i].v]++;
34      }
35 }
36 int main()
37 {
38     int i,j,flag,t;
39     scanf("%d",&t);
40     while (t--)
41     {
42         scanf("%d%d",&n,&m);
43         flag=0;
44         memset(v,0,sizeof(v));
45         memset(v1,0,sizeof(v1));
46         memset(v2,0,sizeof(v2));
47         for (i=1;i<=m;i++)
48         {
49            scanf("%d%d",&s[i].u,&s[i].v);
50            v[s[i].u]++;
51            v[s[i].v]++;
52         }
53         for (i=1;i<=n;i++)
54         {
55            if (v[i]%2==1)
56            {
57               flag=1;
58               break;
59            }
60            v1[i]=v2[i]=v[i]/2;
61         }
62         ans=0;
63         dfs(1);
64         printf("%d
",ans);
65     }
66 }

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