明明O(n^3),为何会TLE

#include<bits/stdc++.h>
using namespace std;
template<typename T> inline void read(T& x){
    x=0;int f=1;
    char ch=getchar();
    while(!isdigit(ch)){if(ch=='-') f=~f+1;ch=getchar();}
    while(isdigit(ch)){x=(x<<3)+(x<<1)+(ch^48);ch=getchar();}
    x*=f;
}
template<typename T,typename... Args>inline void read(T& x,Args&... args){
    read(x);
    read(args...);
}
template<typename T>inline void write(T x){
    static int buf[40],top=0;
    if(x<0){putchar('-');x=~x+1;}
    while(x)buf[++top]=x%10,x/=10;
    if(top==0)buf[++top]=0;
    while (top) putchar(buf[top--]^48);
    putchar(' ');
}
template<typename T,typename... Args>inline void write(T x,Args... args){
    write(x);
    write(args...);
}
int n,m,s,a[1010],in[1010],ans;
int used[1010],cnt,tail[1010];
struct node{
    int u,v,next;
}ed[1010];
struct node1{
    int dep,id;
};
void add(int u,int v){
    ed[++cnt].u=u;
    ed[cnt].v=v;
    ed[cnt].next=tail[u];
    tail[u]=cnt;
}
queue<node1>q;
int main(){
    read(n);read(m);
    for(int i=1;i<=n;i++){
        in[i]=-1;
    }
    for(int i=1;i<=m;i++){
        read(s);
        for(int i=1;i<=n;i++){
            used[i]=0;
        }
        for(int j=1;j<=s;j++){
            read(a[j]);
            used[a[j]]++;
        }
        for(int j=a[1];j<=a[s];j++){
            if(in[j]==-1)in[j]=0;
            if(used[j]==0){
                for(int k=1;k<=s;k++){
                    add(a[k],j);
                    in[j]++;
                }
            }
        }
    }
    for(int i=1;i<=n;i++){
        if(in[i]==0)q.push({1,i});
    }
    while(!q.empty()){
        node1 now=q.front();
        q.pop();
        if(in[now.id]==-1)continue;
        in[now.id]=-1;
        ans=max(ans,now.dep);
        for(int i=tail[now.id];i;i=ed[i].next){
            int to=ed[i].v;
            in[to]--;
            if(in[to]==0){
                q.push({now.dep+1,to});
            }
        }
    }
    write(ans);
    return 0;
}