Go: package main

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

// I/O
type Scanner struct {
	sc *bufio.Scanner
}

func NewScanner() *Scanner {
	sc := bufio.NewScanner(os.Stdin)
	sc.Split(bufio.ScanWords)
	sc.Buffer(make([]byte, 1024), int(1e+9))
	return &Scanner{sc}
}

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

func (s *Scanner) nextInt() int {
	i, e := strconv.Atoi(s.nextStr())
	if e != nil {
		panic(e)
	}
	return i
}

func (s *Scanner) nextFloat() float64 {
	f, e := strconv.ParseFloat(s.nextStr(), 64)
	if e != nil {
		panic(e)
	}
	return f
}

func (s *Scanner) nextRuneSlice() []rune {
	return []rune(s.nextStr())
}

func (s *Scanner) nextIntSlice(n int) []int {
	res := make([]int, n)
	for i := 0; i < n; i++ {
		res[i] = s.nextInt()
	}
	return res
}

func (s *Scanner) nextFloatSlice(n int) []float64 {
	res := make([]float64, n)
	for i := 0; i < n; i++ {
		res[i] = s.nextFloat()
	}
	return res
}

// Arithmetic
func max(nums ...int) int {
	m := nums[0]
	for _, i := range nums {
		if m < i {
			m = i
		}
	}
	return m
}

func min(nums ...int) int {
	m := nums[0]
	for _, i := range nums {
		if m > i {
			m = i
		}
	}
	return m
}

func abs(x int) int {
	if x > 0 {
		return x
	}
	return -x
}

func pow(x, y int) int {
	res := 1
	for i := 0; i < y; i++ {
		res *= x
	}
	return res
}

func ceil(a, b int) int {
	if a%b == 0 {
		return a / b
	} else {
		return a/b + 1
	}
}

// Sort
type RuneSlice []rune

func (a RuneSlice) Len() int           { return len(a) }
func (a RuneSlice) Less(i, j int) bool { return a[i] < a[j] }
func (a RuneSlice) Swap(i, j int)      { a[i], a[j] = a[j], a[i] }

// Main
type Queue struct {
	arr []int
}

func (q *Queue) push(v int) {
	q.arr = append(q.arr, v)
}

func (q *Queue) pop() int {
	res := q.arr[0]
	q.arr = q.arr[1:]
	return res
}

func (q *Queue) isEmpty() bool {
	return len(q.arr) == 0
}

func main() {
	sc := NewScanner()
	wtr := bufio.NewWriter(os.Stdout)
	N := sc.nextInt()
	G := make([][]int, N)
	for i := 0; i < N; i++ {
		u, k := sc.nextInt()-1, sc.nextInt()
		for j := 0; j < k; j++ {
			G[u] = append(G[u], sc.nextInt()-1)
		}
	}
	var q Queue
	seen := make([]int, N)
	for i := 0; i < N; i++ {
		seen[i] = -1
	}
	var search func(cur int)
	search = func(cur int) {
		for i := 0; i < len(G[cur]); i++ {
			next := G[cur][i]
			if seen[next] == -1 {
				q.push(next)
				seen[next] = seen[cur] + 1
			}
		}
	}
	q.push(0)
	seen[0] = 0
	for !q.isEmpty() {
		search(q.pop())
	}

	for i := 0; i < N; i++ {
		fmt.Fprintln(wtr, i+1, seen[i])
	}
	wtr.Flush()
}

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

using namespace std;
static const int N = 100;
static const int INFTY = -1;

int n, M[N][N];
int d[N];

void bfs(int s)
{
	queue<int> q;
	q.push(s);
	for(int i=0; i<n; i++)
	{
		d[i]=INFTY;
	}
	d[s]=0;
	int u;
	while(!q.empty())
	{
		u=q.front();
		q.pop();
		for(int v=0; v<n; v++)
		{
			if(M[u][v]==0)
				continue;
			if(d[v]!=INFTY)//已经在前面遍历过 
				continue;
			d[v]=d[u]+1;
			q.push(v);
		}		 
	}
	for(int i=0; i<n; i++)
	{
		cout<<i+1<<" "<<((d[i]==INFTY) ? (-1) : (d[i]))<<endl;
	}
}

int main()
{
	int u, k, v;
	cin>>n;
	for(int i=0; i<n; i++)
	{
		for(int j=0; j<n; j++)
		{
			M[i][j]=0;
		}
	}
	for(int i=0; i<n; i++)
	{
		cin>>u>>k;
		u--;
		for(int j=0; j<k; j++)
		{
			cin>>v;
			v--;
			M[u][v]=1;
		}
	}
	bfs(0);
	return 0;
}

C++: #include <algorithm>
#include <iostream>
#include <queue>
#include <string>
using namespace std;
static const int MAX = 100;
int N;
int ADJ[MAX][MAX];
int depth[MAX] = {0};

enum STATUS { ACTIVE = 0, MARKED, VISITED, };
int status[MAX] = {ACTIVE};

void visit(int id) {
  status[id] = VISITED;
}
void mark(int id) {
  status[id] = MARKED;
}

void bfs(int id) {
  queue<int> q;
  q.push(id);
  depth[id] = 0;

  while (!q.empty()) {
    int u = q.front();
    q.pop();
    visit(u);
    for (int i = 0; i < N; i++) { 
      if (ADJ[u][i] && status[i] == ACTIVE) {
        q.push(i);
        mark(i);
        depth[i] = depth[u] + 1;
      }
    }
  }
}

int main() {
  cin >> N;
  int id, nn, x;
  for (int i = 0; i < N; i++) {
    cin >> id >> nn;
    id--; // 0-based
    for (int j = 0; j < nn; j++) {
      cin >> x;
      x--; // 0-based
      ADJ[id][x] = 1;
    }
  }

  bfs(0);
  for (int i = 0; i < N; i++)
    cout << i << " " << depth[i] << endl;
}

C++: #include <bits/stdc++.h>
using namespace std;

#define vv vector< vector< int > >
#define ll long long


int main(){
    int n;
    cin >> n;
    vv tree(n);
    for(int i = 0; i < n; ++i){
        int a, k;
        cin >> a >> k;
        a--;
        for(int j = 0; j < k; ++j){
            int b;
            cin >> b;
            b--;
            tree[a].push_back(b);
        }
    }
    vector<int> dist(n, -1);
    queue<int> que;
    dist[0] = 0;
    que.push(0);

    while(!que.empty()){
        int v = que.front();
        que.pop();

        for (int nv : tree[v]){
            if(dist[nv] != -1) continue;
            dist[nv] = dist[v] + 1;
            que.push(nv);
        }
    }
    for(int v = 0; v < n; v++) cout << v+1 << " " << dist[v] << endl;
    return 0;
}

C++: #include<bits/stdc++.h>
using namespace std;
vector<int> graph[105];
bool vis[105];
int lvl[105];
int i;
void bfs(int rt)
{
    int src,adj;
    src=rt;
    deque<int>dq;
    vis[src]=1;
    lvl[src]=1;
    dq.push_back(src);
    while(!dq.empty())
    {
        src=dq.front();
        dq.pop_front();
        for(i=0; i<graph[src].size(); i++)
        {
            adj=graph[src][i];
            if(vis[adj]==0)
            {
                vis[adj]=1;
                lvl[adj]=lvl[src]+1;
                dq.push_back(adj);
            }
        }
    }
}
int main()
{
    int nodes,x,v;
    cin >> nodes;
    int u[200];
    memset(vis,0,sizeof(vis));
    memset(lvl,0,sizeof(lvl));
    for(i=1;i<=nodes;i++)
    {
        cin >> u[i];
        cin >> x;
        for(int j=0;j<x;j++)
        {
            cin >> v;
            graph[u[i]].push_back(v);
        }
    }
    bfs(1);
    for(i=1;i<=nodes;i++)
    {
        cout << u[i] << " " << lvl[u[i]]-1 << endl;
    }
}

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

using namespace std;

enum COLOR {
  WHITE,
  GRAY,
  BLACK,
};

static const int INFTY = INT_MAX;
static const int N = 100;

static int M[N][N] = {};
static vector<COLOR> color(N, WHITE);
static vector<int> d(N, INFTY);

static void bfs(int n, int s) {
  color[s] = GRAY;
  d[s] = 0;

  queue<int> Q;
  Q.push(s);

  while (!Q.empty()) {
    int u = Q.front();
    Q.pop();
    for (int v = 0; v < n; v++) {
      if (M[u][v] && color[v] == WHITE) {
          color[v] = GRAY;
          d[v] = d[u] + 1;
          Q.push(v);
      }
      color[u] = BLACK;
    }
  }
}

int main() {
  int n;
  cin >> n;

  int number, count, value;
  for (int i = 0; i < n; i++) {
    cin >> number >> count;
    number--;
    for (int j = 0; j < count; j++) {
     cin >> value;
     value--;
     M[number][value] = 1; 
    }
  }
  
  bfs(n, 0);
  
  for (int i = 0; i < n; i++) {
    cout << i + 1 << " " << ((d[i] == INFTY) ? -1 : d[i]) << endl; 
  }

  return 0;
}

C++: #include<iostream>
#include<algorithm>
using namespace std;

struct VRTX {
	int v[100] = {}, dist = -1;
};

int n, curdist = 0;
VRTX u[100];

void breadthFirstSearch(int x, int dist);

int main() {
	int i, j, id, dim;
	
	cin >> n;
	for (i = 0; i < n; i++) {
		cin >> id >> dim;
		for (j = 0; j < dim; j++) {
			cin >> u[id].v[j];
		}
	}

	breadthFirstSearch(1, 0);

	for (i = 1; i <= n; i++) {
		cout << i << " " << u[i].dist << endl;
	}

	return 0;
}

void breadthFirstSearch(int x, int dist) {
	int i, nextdist;

	if (u[x].dist == -1)u[x].dist = dist;
	else u[x].dist = min(u[x].dist, dist);
	
	i = 0;
	nextdist = u[x].dist + 1;
	while (u[x].v[i] != 0) {
		breadthFirstSearch(u[x].v[i], nextdist);
		i++;
	}
}