求助

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;
}