2015 Multi-University Training Contest 2

#include<cstdio>
#include<cstring>
#include<algorithm>

using namespace std;

struct data
{
int u,v;
}e[100];

int n,m,in[10],ans,a[10],b[10];

void dfs(int x)
{
int i,u,v;
if(x==m)
    {
for(i=1;i<=n;i++)
        {
if(a[i]!=0||b[i]!=0) break;
        }
if(i>n) ans++;
return ;
    }
u=e[x].u;
v=e[x].v;
if(a[u]>0&&a[v]>0)
    {
a[u]--;
a[v]--;
dfs(x+1);
a[u]++;
a[v]++;
    }
if(b[u]>0&&b[v]>0)
    {
b[u]--;
b[v]--;
dfs(x+1);
b[u]++;
b[v]++;
    }
return ;
}
int main()
{
int _,i,j,u,v,f;
scanf("%d",&_);
while(_--)
    {
memset(in,0,sizeof(in));
memset(a,0,sizeof(a));
memset(b,0,sizeof(b));
scanf("%d%d",&n,&m);
for(i=0;i<m;i++)
        {
scanf("%d%d",&u,&v);
e[i].u=u;
e[i].v=v;
in[u]++;
in[v]++;
        }
f=0;
for(i=1; i<=n; i++)
        {
if(in[i]%2==1)
            {
f=1;
break;
            }
else
            {
a[i]=b[i]=in[i]/2;
            }
        }
if(m%2==1||f==1)
        {
printf("0\n");
continue;
        }
ans=0;
dfs(0);
printf("%d\n",ans);
    }
return 0;
}