cf 757C. Felicity is Coming!

这个题还是比较劲的（题意太神了），才知道vector还可以==和排序，扒题解大法好！！

 #include<bits/stdc++.h>
 #define lowbit(x) x&(-x)
 #define LL long long
 #define N 200005
 #define M 1000005
 #define mod 1000000007LL
 #define inf 0x7ffffffff
 using namespace std;
 inline int ra()
 {
     int x=,f=; char ch=getchar();
     while (ch<'' || ch>''){if (ch=='-') f=-; ch=getchar();}
     while (ch>='' && ch<=''){x=x*+ch-''; ch=getchar();}
     return x*f;
 }
 vector<int> a[M];
 int main()
 {
     int n=ra(),m=ra();
     for (int i=; i<=n; i++)
     {
         int num=ra();
         while (num--)
         {
             int x=ra();
             a[x].push_back(i);
         }
     }
     sort(a+,a+m+);
     LL ans=,f=;
     for (int i=; i<=m; i++)
         if (a[i]==a[i-])
         {
             f++;
             ans=(ans*f)%mod;
         }
         else f=;
     cout<<ans;
     return ;
 }