虚点做法

#include<cstdio>
#include<queue>
#include<cstring>
using namespace std;
const int N=1005;
int n,m,ans=0;
bool vis[N*N];
int du[N],f[N*N];
int hd[N*N],nt[N*N],e[N*N],cnt=0;
inline int maxx(int x,int y){return x>=y?x:y;}
inline void tian(int x,int y){
	e[++cnt]=y,nt[cnt]=hd[x],hd[x]=cnt;
	du[y]++;
}
inline void topo(){
	queue<int> q;
	int p=m+n;
	for(int i=1;i<=p;i++){
		if(!du[i]){
			q.push(i);
			if(i<=n) f[i]=1;
			else	 f[i]=0;
		}
	}
	while(q.size()){
		int x=q.front();   q.pop();
		for(int i=hd[x];i;i=nt[i]){
			int y=e[i];
			if(y<=n) f[y]=maxx(f[x]+1,f[y]);
			else	 f[y]=maxx(f[x],f[y]);
			ans=maxx(ans,f[y]);
			if(--du[y]==0)
				q.push(y);
		}
	}
}
int main(){
	scanf("%d%d",&n,&m);
	for(int i=1;i<=m;i++){
		memset(vis,0,sizeof(vis));
		int s;scanf("%d",&s);
		int tou,wei,xu=n+i;
		for(int j=1;j<=s;j++){
			int a;scanf("%d",&a);
			if(j==1) tou=a;
			if(j==s) wei=a;
			vis[a]=1;
			tian(xu,a);
		}
		for(int j=tou;j<=wei;j++)
			if(!vis[j]) tian(j,xu);
	}
	topo();
	printf("%d",ans);
	return 0;
}