题目
题目链接：https://www.luogu.com.cn/problem/P1346
代码
#include<cstdio>
#include<cstring>
#include<cmath>
#include<cstdlib>
#include<cctype>
#include<ctime>
#include<iostream>
#include<string>
#include<map>
#include<queue>
#include<stack>
#include<set>
#include<vector>
#include<iomanip>
#include<list>
#include<bitset>
#include<sstream>
#include<fstream>
#include<complex>
#include<algorithm>
#if __cplusplus >= 201103L
#include <unordered_map>
#include <unordered_set>
#endif
#define ll long long
using namespace std;
const int INF = 0x3f3f3f3f;
int d[300][300];
int main(){
ios::sync_with_stdio(false);cin.tie(0);cout.tie(0);
int n,a,b;
cin>>n>>a>>b;
memset(d,INF,sizeof d);
for(int i=1;i<=n;i++){
int m;
cin>>m;
for(int j=1;j<=m;j++){
int b;
cin>>b;
if(j==1) d[i][b]=0;
else d[i][b]=1;
}
}
for(int k=1;k<=n;k++){
for(int i=1;i<=n;i++){
for(int j=1;j<=n;j++){
if(d[i][j]>d[i][k]+d[k][j]){
d[i][j]=d[i][k]+d[k][j];
}
}
}
}
if(d[a][b]==INF) cout<<"-1"<<endl;
else cout<<d[a][b]<<endl;
return 0;
}