dfs写法，为什么前面20分拿不到

#include <bits/stdc++.h>
#define ll long long
#define mem(a,v) memset(a,v,sizeof(a))
using namespace std;
const int maxm = 1e5+5;
int T,n,m,v,c[maxm],d[maxm],a[maxm],b[maxm],x[maxm],ans; 
int dx[] = {1,2,1,2};
int dy[] = {1,2,2,1};
bool cbh = false;
void dfs2(int cnt)
{
	if(cbh) return;
	if(cnt == n+1)
	{
		for(int i = 1;i < n;++i)
			if(x[i] == a[i] && x[i+1] != b[i]) return;
		ans++;
		cbh = true;
		return;
	}	
	if(x[cnt]) dfs2(cnt+1);
	else
	{
		x[cnt] = 1;
		dfs2(cnt+1);
		x[cnt] = 2;
		dfs2(cnt+1);
	}
} 
void dfs(int cnt)
{
	if(cnt == n)
	{
		cbh = false;
		dfs2(1);
		return;
	}
	for(int i = 0;i < 4;++i)
	{
		a[cnt] = dx[i],b[cnt] = dy[i];
		dfs(cnt+1);
	}
}
int main(int argc,char *argv[])
{
	scanf("%d",&T);
	while(T--)
	{
		ans = 0;
		mem(a,0);mem(b,0);mem(c,0);mem(d,0);mem(x,0);
		scanf("%d%d%d",&n,&m,&v);
		for(int i = 1;i <= m;++i)
		{
			scanf("%d%d",&c[i],&d[i]);
			if(!x[c[i]]) x[c[i]] = d[i];
			else if(x[c[i]] != d[i])
			{
				//cout<<"fuck";
				puts("0");
				goto nxt;
			}
		}
			
		dfs(1);
		printf("%d\n",ans);
		nxt:continue;
	}
	return 0;
}