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<vector>
#include<queue>
#include<stack>
#include<map>
#include<string>
#include<algorithm>
#include<utility>
#include<math.h>
using namespace std;
typedef long long int ll;
typedef pair<int, int> P;
const int INF = pow(10, 8);
int main(){
  int n;cin>>n;
  vector<vector<int> > edge(n, vector<int>());
  for(int i=0;i<n;i++){
    int u, k;cin>>u>>k;u--;
    for(int j=0;j<k;j++){
      int v;cin>>v;edge[i].push_back(v-1);
    }
  }
  vector<int> dis(n, INF);
  dis[0]=0;
  queue<int> que;
  que.push(0);
  while(que.size()){
    int v = que.front();que.pop();
    for(int &u : edge[v]){
      if(dis[u]>dis[v]+1){
        dis[u]=dis[v]+1;
        que.push(u);
      }
    }
  }
  for(int i=0;i<n;i++){
    if(dis[i]==INF)cout<<i+1<<" "<<-1<<endl;
    else cout<<i+1<<" "<<dis[i]<<endl;
  }
  return 0;
}

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

int n,v,u,k,d=0;
int l[110],f[110];
int b[110][110];
queue<int> q;
void bfs(int a)
{
	while(!q.empty()){
		a=q.front();q.pop();
		for(int i=1;i<=n;i++){
			if(b[a][i]==1&&f[i]==0){
				f[i]=1;
				q.push(i);
				l[i]=l[a]+1;
			}
		}
	}
	return ;
}
int main()
{	
	cin>>n;
	for(int i=1;i<=n;i++){
		cin>>u;
		cin>>k;
		for(int j=1;j<=k;j++){
			cin>>v;
			//cout<<v<<endl;
			b[u][v]=1;
		} 
	}
	
	
	//cout<<"@"<<b[1][3]<<"@"<<endl;
	l[1]=0;
	f[1]=1;
	q.push(1);
	bfs(1);
	for(int i=1;i<=n;i++){
		if(l[i]==0&&i!=1){
			cout<<i<<" "<<-1<<endl;
			continue;
		}
		cout<<i<<" "<<l[i]<<endl;
	}
	return 0;
 }

C++: //
//  main.cpp
//  breadth_first_search
//
//  Created by ???????????? on 2017/10/22.
//  Copyright ?? 2017 ????????????. All rights reserved.
//

#include <iostream>
#include <stdio.h>
#include <queue>

#define n_max 100
#define INFTY 1000
#define WHITE 0
#define GRAY 1
#define BLACK 2

using namespace std;

int M[n_max][n_max], color[n_max], d[n_max], n;

queue<int> Q;

void encode_graph(){
    int i, j, id, num, node;
    
    //initialize with 0
    for(i = 0; i < n; i++){
        for(j = 0; j < n; j++){
            M[i][j] = 0;
        }
    }
    
    for (i = 0; i < n; i++){
        scanf("%d", &id);
        scanf("%d", &num);
        for(j = 0; j < num; j++){
            scanf("%d", &node);
            M[id-1][node-1] = 1;
        }
    }
}

void bfs(){
    for(int i = 0; i < n ; i++){
        color[i] = WHITE;
        d[i] = INFTY;
    }
    //starting point
    int s = 0;
    color[s] = GRAY;
    d[s] = 0;
    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 argc, const char * argv[]) {
    scanf("%d", &n);
    
    encode_graph();
    bfs();
    
    for(int i = 0; i < n; i++){
        cout<<i+1<<" "<<((d[i] == INFTY) ? (-1): (d[i]))<<endl;
    }
    
//    std::cout << "Hello, World!\n";
    return 0;
}

C++: #include<iostream>
#include<algorithm>
#include<vector>
#include<cassert>
#include<cstdio>
#include<queue>

using namespace std;

int N, G[100][100], V[100], D[100];//G:２頂点,V:次数,D:距離

void bfs(int src){
	queue<int> Q;
	Q.push(src);
	fill(D, D + N, -1);
	D[src] = 0;
	while (!Q.empty()){
		int cur = Q.front();
		Q.pop();
		for (int k = 0; k < N; k++){
			if (G[cur][k] == 1 && D[k] == -1){
				D[k] = D[cur] + 1;
				Q.push(k);
			}
		}
	}
	for (int l = 0; l < N; l++){
		cerr << l + 1 << " " << D[l] << endl;
	}
}

int main(){
	scanf_s("%d", &N);
	int id, c;
	for (int i = 0; i < N; i++){
		scanf_s("%d", &id); id--;//配列は0から始まるので、頂点番号を-1して考える。
		scanf_s("%d", V + id);
		for (int j = 0; j < V[id]; j++){
			scanf_s("%d", &c); c--;//配列は0から始まるので、頂点番号を-1して考える。
			G[id][c] = 1;
		}
	}//データの読み込み完了。
	bfs(0);
}

C++: #include <iostream>
#include <algorithm>
#include <vector>
#include <string>
#include <complex>
#include <stack>
#include <queue>
#include <list>
#include <unordered_map>
#include <utility>
#include <map>
#include <set>
using namespace std;

int main(){
    int n;
    cin >> n;
    int g[110][110];
    int i, j;
    int u, k, v;
    int dist[110];
    bool visited[110];
    
    for(i = 0; i < n; i++){
        dist[i] = -1;
        for(j = 0; j < n; j++){
            g[i][j] = 0;
        }
    }
    
    for(i = 0; i < n; i++){
        cin >> u >> k;
        u--;
        for(j = 0; j < k; j++){
            cin >> v;
            v--;
            g[u][v] = 1;
        }
    }
    
    queue<int> q1, q2;
    q1.push(0);
    
    for(i = 0; q1.size(); i++){
        while(!q1.empty()){
            int p = q1.front();
            q1.pop();
            
            if(visited[p]) continue;
            visited[p] = true;
            
            dist[p] = i;
            
            for(j = 0; j < n; j++){
                if(g[p][j]){
                    q2.push(j);
                }
            }
        }
        q1 = q2;
        while(!q2.empty()){
            q2.pop();
        }
    }
    
    for(i = 0; i < n; i++){
        printf("%d %d\n", i+1, dist[i]);
    }
}

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

using namespace std;

template <class T>
struct Edge {
    int to;
    T cost;
    Edge(int to, T cost) : to(to), cost(cost){};
};

template <class T = int>
class Graph {
public:
    explicit Graph(int N = 0) : size(N) { path.resize(size); }
    void span(int u, int v, T cost = 1) { path[u].push_back(Edge<T>(v, cost)); }
    vector<Edge<T>> operator[](int v) const { return path[v]; }

    int size;
    vector<vector<Edge<T>>> path;
};

template <class T>
vector<T> bfs(const Graph<>& graph, int s) {
    vector<int> dist(graph.size, -1);
    dist[s] = 0;
    queue<int> que;
    que.push(s);

    while (!que.empty()) {
        int v = que.front();
        que.pop();
        for (auto e : graph[v]) {
            if (dist[e.to] < 0) {
                dist[e.to] = dist[v] + 1;
                que.push(e.to);
            }
        }
    }
    return dist;
}

int main() {
    int N;
    cin >> N;
    Graph<> graph(N);
    for (int i = 0; i < N; ++i) {
        int v, k;
        cin >> v >> k;
        --v;
        for (int j = 0; j < k; ++j) {
            int sv;
            cin >> sv;
            graph.span(v, --sv);
        }
    }

    auto dist = bfs<int>(graph, 0);
    for (int v = 0; v < N; ++v) {
        cout << v + 1 << " " << dist[v] << endl;
    }
    return 0;
}