Go: package main

import (
	"bufio"
	"fmt"
	"os"
	"strconv"
)

func main() {
	scn := bufio.NewScanner(os.Stdin)
	scn.Split(bufio.ScanWords)
	nextInt := func() int { scn.Scan(); r, _ := strconv.Atoi(scn.Text()); return r }
	w := bufio.NewWriter(os.Stdout)

	n := nextInt()
	vecs := make([][]int, n)
	for i := 0; i < n; i++ {
		u := nextInt()
		k := nextInt()
		for j := 0; j < k; j++ {
			vecs[u-1] = append(vecs[u-1], nextInt()-1)
		}
	}

	ds := make([]int, 0, n)
	for i := 0; i < n; i++ {
		ds = append(ds, -1)
	}

	q := make([]int, 0, n)
	q = append(q, 0)
	ds[0] = 0

	for len(q) > 0 {
		i := pop(&q)
		for _, v := range vecs[i] {
			if ds[v] == -1 {
				ds[v] = ds[i]+1
				q = append(q, v)
			}
		}
	}

	for i, d := range ds {
		fmt.Fprintln(w, i+1, d)
	}

	w.Flush()
}

func pop(q *[]int) int {
	v := (*q)[0]
	*q = (*q)[1:]
	return v
}

C++: #include <iostream>
#include <queue>
using namespace std;
const int MAX_N = 100;

int A[MAX_N+1][MAX_N+1];
int D[MAX_N+1];
int N;

void solve() {
  int d;
  queue<int> Q;

  Q.push(1);
  D[1] = d = 0;

  while (!Q.empty()) {
    int c = Q.front(); Q.pop();

    for (int i = 1; i <= N; i++) {
      if (A[c][i] == 1 && D[i] == -1) {
        D[i] = D[c]+1;
        Q.push(i);
      }
    }
  }
}

int main() {
  cin >> N;

  for (int i = 1; i <= N; i++) {
    for (int j = 1; j <= N; j++) {
      A[i][j] = 0;
    }
    D[i] = -1;
  }

  for (int i = 0; i < N; i++) {
    int u, k; cin >> u >> k;
    for (int j = 0; j < k; j++) {
      int t; cin >> t;
      A[u][t] = 1;
    }
  }

  solve();

  for (int i = 1; i <= N; i++) {
    cout << i << ' ' << D[i] << endl;
  }

  return 0;
}

C++: # include <iostream>
# include <vector>
# include <cstdio>
# include <queue>
using namespace std;
struct info
{
	int d = -1;
	bool vis = false;
};
vector<int> a[105];
info *ans;
queue<int> solve;
void bfs()
{
	solve.push(1); 
	ans[1].vis = true; ans[1].d = 0;
	while(!solve.empty())
	{
		int u = solve.front(); solve.pop();
		for(int j = 0;j < a[u].size();j++)
		{
			if(!ans[a[u][j]].vis)
			{
				ans[a[u][j]].vis = true;
				ans[a[u][j]].d = ans[u].d + 1;
				solve.push(a[u][j]);
			}
		}
	}
	
}
int main(void)
{
	int n,cnt,k,u;
	scanf("%d",&n);
	ans = new info [n+1];
	for(int w = 0;w < n;w++)
	{
		scanf("%d %d",&u,&cnt);
		for(int i = 0;i < cnt;i++)
		{
			scanf("%d",&k);
			a[u].push_back(k);
		}
	}
	bfs();
	for(int i = 1;i <= n;i++) printf("%d %d\n",i,ans[i].d);
	return 0;
}

C++: 
#pragma GCC optimize("O3")
#include <bits/stdc++.h>
#define ll long long
#define rep2(i,a,b) for(ll i=a;i<=b;++i)
#define rep(i,n) for(ll i=0;i<n;i++)
#define rep3(i,a,b) for(ll i=a;i>=b;i--)
#define pii pair<int,int>
#define pll pair<ll,ll>
#define pq priority_queue
#define pb push_back
#define eb emplace_back
#define veci vector<int>
#define vecll vector<ll>
#define vecpii vector<pii>
#define vec2(a,b) vector<vec>(a,vec(b))
#define vec2ll(a,b) vector<vec>(a,vecll(b))
#define vec3(a,b,c) vector<vector<vec>>(a,vec2(b,c))
#define vec3ll(a,b,c) vector<vector<vecll>>(a,vec2ll(b,c))
#define fi first
#define se second
#define all(c) begin(c),end(c)
#define ios ios_base::sync_with_stdio(0),cin.tie(0),cout.tie(0);
#define lb(c,x) distance(c.begin(),lower_bound(all(c),x))
#define ub(c,x) distance(c.begin(),upper_bound(all(c),x))


using namespace std;
int in() {int x;cin>>x;return x;}
ll lin() {ll x;cin>>x;return x;}
template<class T> inline bool chmax(T& a,T b){if(a<b){a=b;return 1;}return 0;}
template<class T> inline bool chmin(T& a,T b){if(a>b){a=b;return 1;}return 0;}
template<class T> inline void print(pair<T,T> p){cout<<"("<<p.first<<","<<p.second<<") ";}
//template<class T> inline void print(vector<pair<T,T>> v){for(auto e:v)print(e); cout<<endl;}
//template<class T> inline void print(T v){for(auto e:v)cout<<e<<" ";cout<<endl;}
template<typename T>
istream& operator >> (istream& is, vector<T>& vec){
    for(T& x:vec) is >> x;
    return is;
}
const ll INF=1e9+7;

ll m[105][105];
ll d[105];
ll n;


void bfs(ll s){
    queue<ll> q;
    q.push(s);
    rep(i,n){
        d[i]=INF;
    }
    d[s]=0;
    while(!q.empty()){
        ll u=q.front();
        q.pop();
        rep(v,n){
            if(m[u][v]==0) continue;
            if(d[v]!=INF) continue;
            d[v]=d[u]+1;
            q.push(v);
        }
    }
    rep(u,n){
        cout << u+1 << " " << (d[u]==INF?-1:d[u]) << endl;
    }
}

int main()
{
    cin >> n;
    rep(u,n){
        rep(v,n){
            m[u][v]=0;
        }
    }
    ll u,k,v;
    rep(i,n){
        cin >> u >> k;
        u--;
        rep(j,k){
            cin >> v;
            v--;
            m[u][v]=1;
        }
    }
    bfs(0);
    return 0;
}

C++: /**
 * Bredth first search.
 */

#include <iostream>
using namespace std;
const int N = 101;
int adj[N][N] = {0};
int d[N]={0};

void bfs(int n, int dd) {
	int k = adj[n][0];
	d[n] = dd++;
	for (int j=1;j<=k;j++) {
		bfs(adj[n][j], dd);
	}
}

int main()
{
	int n;
	cin >> n;
	for (int i=1;i<=n;i++){
		int j, k;
		cin >> j >> k;
		adj[j][0]=k;
		for (int m=1;m<=k;m++) {
			int a;
			cin >> a;
			adj[j][m]=a;
		}
	}

	bfs(1, 0);

	for (int i=1;i<=n;i++){
		cout << i << ' ' << d[i] << endl;
	}

	return 0;
}

C++: #include<iostream>
#define INF 1000000
using namespace std;

int que[100000];
int head,tail,leng=100000;
 
int isEmpty(){
  return head==tail;
}
 
void enqueue(int x){
  que[tail]=x;
  if(tail+1==leng) tail=0;
  else tail++;
}
 
int dequeue(){
  int x;
  x=que[head];
  if(head+1==leng) head=0;
  else head++;
  return x;
}
 

int a[101][101];
int d[101];
int n;

void bfs(int s){
int t;
  for(int i=1;i<=n;i++)d[i]=INF;
  d[s]=0;
   while(!isEmpty()){
    t=dequeue();
    for(int i=1;i<=n;i++){
      if(d[i]!=INF || a[t][i]!=1) continue;
       enqueue(i),d[i]=d[t]+1;
    }
  }
}

int main(){
  int top,m,s;
  cin>>n;
  for(int i=0;i<n;i++){
    cin>>top>>m;
    for(int j=0;j<m;j++)
      cin>>s,a[top][s]=1;
     } 
  enqueue(1);
   bfs(1);
   for(int i=1;i<=n;i++){
     if(d[i]==INF) d[i]=-1;
     cout<<i<<" "<<d[i]<<endl;
   }
    return 0;
}