HDU 5305Friend

#include <cstdio>  
#include <cstring>  
bool mp[10][10];
int deg[10], c1[10], c2[10];//c1[i]表示i的在线朋友数，c2[i]表示i的离线朋友数
int n, m, cnt, ans;


struct EDGE
{
int u, v;
}e[100000];


void DFS(int cur)//   DFS边，存着
{
if (cur == m + 1)
{
ans++;
return;
}
int v = e[cur].v;
int u = e[cur].u;
if (c1[u] && c1[v])
{
c1[u] --;
c1[v] --;
DFS(cur + 1);
c1[u] ++;//回溯
c1[v] ++;
}
if (c2[u] && c2[v])
{
c2[u] --;
c2[v] --;
DFS(cur + 1);
c2[u] ++;
c2[v] ++;
}
return;
}


int main()
{
int T;
scanf("%d", &T);
while (T--)
{
cnt = 0;
ans = 0;
memset(deg, 0, sizeof(deg));
memset(e, 0, sizeof(e));
memset(c1, 0, sizeof(c1));
memset(c2, 0, sizeof(c2));
scanf("%d %d", &n, &m);
for (int i = 1; i <= m; i++)
{
scanf("%d %d", &e[i].u, &e[i].v);
deg[e[i].u] ++;
deg[e[i].v] ++;
}
bool f = false;
for (int i = 1; i <= n; i++)
{
c1[i] = c2[i] = deg[i] / 2;
if (deg[i] & 1)
{
f = true;
break;
}
}
if (f)
{
printf("0\n");
continue;
}
DFS(1);
printf("%d\n", ans);
}
}