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>
#define INF 1000000
using namespace std;
class st
{
	public:
		int vertex;
		int dis;
	st();
	st(int,int);
};

st::st()
{
	vertex=-1;
	dis=-1;
}

st::st(int v,int d)
{
	vertex=v;
	dis=d;
}

int main()
{
	int n;
	cin>>n;
	int g[101][101];
	for(int i=0;i<=n;i++)
		for(int j=0;j<=n;j++)
		{
			if (i==j)
				g[i][j]=0;
			else
				g[i][j]=INF;
		}
	for(int i=0;i<n;i++)
	{
		int f,en;
		cin>>f>>en;
		for(int j=0;j<en;j++)
		{
			int t;
			cin>>t;
			g[f][t]=1;

		}
	}

/*	for(int i=1;i<=n;i++)
	{
		for(int j=1;j<=n;j++)
			cout<<g[i][j]<<" ";
		cout<<endl;
	}
*/
	int visited[101];
	for(int i=0;i<=n;i++)
		visited[i]=INF;

	queue<st> Q;
	st first=st(1,0);
	Q.push(first);
	while(!Q.empty())
	{
		st now=Q.front();
		Q.pop();
		for(int i=1;i<=n;i++)
		{
			if(g[now.vertex][i]+now.dis<visited[i])
			{
				visited[i]=g[now.vertex][i]+now.dis;
				Q.push(st(i,visited[i]));
			}
		}
	}
	
	for(int i=1;i<=n;i++)
		cout<<i<<" "<<(visited[i]>=INF?-i:visited[i])<<endl;
	return 0;
}

C++: #include <cmath>
#include <cstdio>
#include <cstring>
#include <cstdlib>
#include <climits>
#include <map>
#include <list>
#include <stack>
#include <queue>
#include <vector>
#include <string>
#include <sstream>
#include <fstream>
#include <iostream>
#include <algorithm>
using namespace std;

int n ,dist[128];
bool rel[128][128];

int main() {
	scanf("%d", &n);
	
	for(int i = 1; i <= n; i++){
		int u, k;
		scanf("%d %d", &u, &k);
		
		dist[u] = INT_MAX;
		for(int j = 1; j <= n; j++){
			rel[u][j] = false;
		}
		while(k--){
			int v;
			scanf("%d", &v);
			rel[u][v] = true;
		}
	}
	
	queue<int> visit;
	visit.push(1);
	dist[1] = 0;
	
	while(visit.size()){
		for(int i = 1; i <= n; i++){
			if(rel[visit.front()][i] && 1 + dist[visit.front()] < dist[i]){
				visit.push(i);
				dist[i] = 1 + dist[visit.front()];
			}
		}
		visit.pop();
	}
	
	for(int i = 1; i <= n; i++){
		printf("%d %d\n", i, dist[i]==INT_MAX ? -1 : dist[i]);
	}
	return 0;
}

C++: def dfs(src)
  D[src] = $time
  (0..N - 1).each do |dst|
    if D[dst] == nil && G[src][dst] == 1
      D[dst] = D[src] + 1
      dfs(dst)
    end
  end
end

N = gets.to_i
G = (1..N).map{ Array.new(N, 0) }
N.times do
  u, k, *v = gets.split(' ').map(&:to_i)
  v.each do |vi|
    G[u - 1][vi - 1] = 1
  end
end

D = Array.new(N) #??????????¨????????????????
# F = Array.new(N) #?????£???????????????


# $time = 1
D[0] = 0

(0..N-1).each do |id|
  dfs(id) unless D[id]
end

(0..N-1).each do |id|
  puts "#{id + 1} #{D[id]}"
end

C++: #include <bits/stdc++.h>
#define rep(i,n) for(int i=0; i<(n); i++)
#define FOR(i,a,n) for(int i=(a); i<(n); i++)
#define all(v) v.begin(), v.end()
#define fi first
#define se second
using namespace std;
using ll = long long;
using vi = vector<int>;
using vl = vector<ll>;
using P = pair<int ,int>;
using Graph = vector<vector<int>>;
const int INF = 1e9;
const int MOD = 1e9+7;

int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);

    int n; cin >> n;
    Graph G(n);
    rep(i, n) {
        int _, k; cin >> _ >> k;
        rep(j, k) {
            int x; cin >> x; x--;
            G[i].push_back(x);
        }
    }

    queue<int> que;
    vector<int> seen(n, -1);
    que.push(0);
    seen[0] = 0;
    while (que.size()) {
        int v = que.front();
        que.pop();
        for(const auto nv: G[v]) {
            if (seen[nv]!=-1) continue;
            seen[nv] = seen[v]+1;
            que.push(nv);
        }
    }
    
    rep(i, n) {
        cout << i+1 << " " << seen[i] << endl;
    }
}