Go: package main

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

//util
var sc = bufio.NewScanner(os.Stdin)

func nextStr() string {
	sc.Scan()
	return sc.Text()
}

func nextInt() int {
	sc.Scan()
	i, e := strconv.Atoi(sc.Text())
	if e != nil {
		panic(e)
	}
	return i
}

func printList(list []int) {
	n := len(list)
	buf := bufio.NewWriter(os.Stdout)
	for _, v := range list[0 : n-1] {
		buf.Write([]byte(fmt.Sprintf("%d ", v)))
	}
	buf.Write([]byte(fmt.Sprintf("%d\n", list[n-1])))
	buf.Flush()
}

func max(a, b int) int {
	if a > b {
		return a
	} else {
		return b
	}
}

func min(a, b int) int {
	if a > b {
		return b
	} else {
		return a
	}
}

//solve
const INFTY = (1 << 21)
const MAX = 100
const WHITE = 0
const GRAY = 1
const BLACK = 2

var time, n int

//隣接行列
var M [MAX][MAX]int

//d[i]: 頂点1から頂点iまでの距離
var color, d [MAX]int

func bfs(s int) {
	var q []int
	q = append(q, s)
	for i := 0; i < n; i++ {
		d[i] = INFTY
	}
	//sは開始点なので、0をいれる
	d[s] = 0

	//キューが空になるまで、以下を繰り返す
	for len(q) > 0 {
		u := q[0]
		q = q[1:]
		for v := 0; v < n; v++ {
			if M[u][v] == 0 {
				continue
			}
			if d[v] != INFTY {
				continue
			}
			d[v] = d[u] + 1
			q = append(q, v)
		}
	}

	for i := 0; i < n; i++ {
		fmt.Printf("%d ", i+1)
		if d[i] == INFTY {
			fmt.Printf("%d\n", -1)
		} else {
			fmt.Printf("%d\n", d[i])
		}
	}
}

func main() {
	sc.Split(bufio.ScanWords)
	n = nextInt()
	for i := 0; i < n; i++ {
		u, k := nextInt(), nextInt()
		M[u-1][u-1] = 0

		//fmt.Println(u, k)
		if k > 0 {
			for j := 0; j < k; j++ {

				v := nextInt()
				M[u-1][v-1] = 1

			}
		}

	}

	bfs(0)

}

C++: //#define _GLIBCXX_DEBUG
#include <bits/stdc++.h>
using namespace std;
#define all(v) v.begin(), v.end()
using in = int64_t;
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define REP(i,a,b) for(int i=(int)(a);i<(int)(b);i++)
const double PI=3.14159265358979323846;
const in MOD = 1000000007;
const in INF=1<<30;
using P=pair<int,int>;
vector<int> dx={0,1,-1,0};
vector<int> dy={1,0,0,-1};

struct edge{int to; int cost;};
vector<vector<edge>> graph(0);
vector<int> d(0);
const int MAX_dist=1e9;

void init(int n){
    graph.resize(n);
    d.resize(n,MAX_dist);
}

void dijkstra(int s){
    priority_queue<P, vector<P>, greater<P>> que;
    d[s]=0;
    que.emplace(0,s);
    while(!que.empty()){
        P p=que.top();
        que.pop();
        int v=p.second;
        if(d[v]<p.first) continue;
        rep(i,graph[v].size()){
            edge e=graph[v][i];
            if(d[e.to]>d[v]+e.cost){
            d[e.to]=d[v]+e.cost;
            que.emplace(d[e.to],e.to);
            }
        }
    }
}

int main(){
ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);
cout << fixed << setprecision(10);
    int n;cin>>n;
    init(n);
    int k,v;
    rep(i,n){
        cin>>k;cin>>k;
        rep(j,k){
            cin>>v;
            graph[i].push_back({v-1,1});
        }
    }
    dijkstra(0);
    rep(i,n){
        cout<<i+1<<" ";
        if(d[i]==MAX_dist) cout<<-1;
        else cout<<d[i];
        cout<<'\n';
    }
}

C++: #include<iostream>
#include<queue>
using namespace std;
int N;
int D[100];
void bfs(int src){
    int u[100],k[100],a[10001],d[100][100];
    bool visit[100];
    for(int i=1;i<=N;++i){
        cin>>u[i]>>k[i];
        for(int j=0;j<k[i];++j){
            cin>>a[j];
            d[u[i]][a[j]]=1;
        }
        visit[i]=true;
    }
    queue<int>Q;
    Q.push(src);
    D[src]=0;
    visit[src]=false;
    while(!Q.empty()){
        int cur=Q.front();
        Q.pop();
        for(int i=1;i<=N;++i){
            if(d[cur][i]==1&&visit[i]){
                visit[cur]=false;
                visit[i]=false;
                D[i]=D[cur]+1;
                Q.push(i);
            }
        }
    }
    for(int i=1;i<=N;++i){
        if(i!=1&&D[i]==0){
            D[i]=-1;
        }
        cout<<i<<" "<<D[i]<<endl;
    }
}
int main(){
    cin>>N;
    int start=1;
    bfs(start);
}

C++: #include <iostream>
#include <vector>
#include <queue>

using namespace std;

const int kSize = 101;

vector<int> adj[kSize];
bool isMarked[kSize];
int d[kSize];

void dfs(int v) {
    isMarked[v] = true;

    for (int i = 0; i < adj[v].size(); ++i) {
        int u = adj[v][i];
        if (!isMarked[u]) {
            dfs(u);
        }
    }
}

void bfs() {
    queue<int> q;
    q.push(1);
    d[1] = 0;
    int dis = 0;
    isMarked[1] = true;

    while (!q.empty()) {
        int size = q.size();
        for (int i = 0; i < size; ++i) {
            int u = q.front();
            q.pop();
            for (int j = 0; j < adj[u].size(); ++j) {
                int v = adj[u][j];
                if (!isMarked[v]) {
                    q.push(v);
                    isMarked[v] = true;
                }
            }

            d[u] = dis;
        }

        dis++;
    }
}

int main() {
    int n;
    fill(isMarked, isMarked + kSize, false);
    cin >> n;
    for (int i = 0; i < n; ++i) {
        int id, k;
        cin >> id >> k;
        for (int j = 0; j < k; ++j) {
            int v;
            cin >> v;
            adj[id].push_back(v);
        }
    }

    bfs();
    for (int i = 1; i <= n; ++i) {
        if (i == 1) {
            cout << i << " " << d[i] << endl;
        } else {
            if (d[i] > 0) {
                cout << i << " " << d[i] << endl;
            } else {
                cout << i << " " << -1 << endl;
            }
        }
    }

    return 0;
}

C++: #include<cstdio>
#include<queue>
#define MAX 100
#define INF 1000
using namespace std;
int n, g[MAX][MAX], labels[MAX], d[MAX];
queue<int> Q;

void bfs(int s) {
    int v,u;
    labels[s] = 1;
    d[s]=0;
    Q.push(s);
    while (!Q.empty()) {
	u = Q.front(); Q.pop();
	for (v=0; v<n; v++) {
	    if (g[u][v] && labels[v]==0) {
		labels[v] =1;
		d[v] = d[u] +1;
		Q.push(v);
	    }
	}
	labels[u] = 2;
    }
}

int main() {
    int i,u,k,v,j;
    scanf("%d",&n);
    for(i=0;i<n;i++){
	for(j=0;j<n;j++){
	    g[i][j]=0;
	}
    }

    for(i=0;i<n;i++){
	scanf("%d %d",&u, &k);
	for(j=0;j<k;j++){
	    scanf("%d",&v);
	    g[u-1][v-1]=1;
	}
    }

    for(i=0; i<n; i++) { labels[i]=0; d[i]=INF;}

    bfs(0);

    for(i=0; i<n; i++) {
	if (d[i] != INF) printf("%d %d\n", i+1, d[i]);
	else printf("%d -1\n", i+1);
    }
    return 0;
}

C++: /**
 * Bredth first search.
 * graphs could be circular.
 * there could be a better answer later.
 */

#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 s[N] = {0}; // this needs to be a stack member.
	int k = adj[n][0];
//	cout << n << ' ' << dd << ' ' << k << endl;
	int kk = 0;
	for (int j=1;j<=k;j++) {
		int nn = adj[n][j];
		if (d[nn] != -1 && d[nn] <= dd) continue; // this condition is important.
		d[nn]=dd;
		s[kk++]=nn;
	//	cout << nn << endl;
	}

	for (int j=0;j<kk;j++)
	{
		bfs(s[j], dd+1);
	}
}

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

	d[1]=0;

	bfs(1, 1);

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

	return 0;
}

C++: #include<iostream>
#include<vector>
#include<queue>
#include<algorithm>
using namespace std;
int main()
{
  queue<int> Q;
  int n,u,k,vv,cur,dst;
  cin >> n;
  vector<int> D(n,-1),check(n,0);
  vector< vector<int> > v(n);
  for(int i = 0;i < n;++i){
    cin >> u >> k;
    for(int j = 0;j < k;++j){
      cin >> vv;
      v[u - 1].push_back(vv);
    }
    sort(v[u - 1].begin(),v[u - 1].end());
  }
  D[0] = 0;
  check[0] = 1;
  Q.push(1);
  while(!Q.empty()){
    cur = Q.front();
    Q.pop();
    for(int i = 0;i < v[cur - 1].size();++i){
      dst = v[cur - 1][i];
      if(check[dst - 1] == 0){
	D[dst - 1] = D[cur - 1] + 1;
	check[dst - 1] = 1;
	Q.push(dst);
      }
    }
  }
  for(int i = 0;i < n;++i)
    cout << i + 1 << " " << D[i] << endl;
}