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()
}

Python: from collections import deque

icase=0
if icase==0:
    n=int(input())
    u=[0]*n
#    g = [deque([]) for _ in range(n)]
    g = [[] for _ in range(n)]
    for i in range(n):
        ukv=list(map(int,input().split()))
        u[i]=ukv[0]-1
        ki=ukv[1]
        v=ukv[2:]
        for vi in v:
            g[u[i]].append(vi-1)
#            g[vi-1].append(u[i])
elif icase==1:
    n=4
    g = [[] for _ in range(n)]
    g[0]=[1,3]
    g[1]=[0,3]
    g[2]=[3]
    g[3]=[0,1,2]
#ans:0 1 2 1

q=deque([0])

stack=[0]
parent=[-1]*n
parent[0]=0
dist=[-1]*n
dist[0]=0
while q:
    state = q.popleft()
#    print("--- q:",q,"state:",state,"g:",g[state],"p:",parent)
    for v in g[state]:
#        print("  state:",state,"v:",v,"q:",q)
#        if parent[state] == v:
        if parent[v] !=-1:
            continue
        else:
#            print("parent:",parent,"xx:",xx,"stack",stack)
            parent[v]=state
            dist[v]=dist[state]+1
            q.append(v)
#            print(" state:",state,"v:",v,"parent:",parent,"stack",stack,"dist[v]",dist[v])

for i in range(n):
    print(i+1,dist[i])

Python: import sys
from collections import deque

inf = 1<<30

def solve():
    n = int(input())
    Adj = [None] * n

    for i in range(n):
        u, k, *line = [int(i) - 1 for i in input().split()]
        Adj[u] = line

    d = bfs(n, Adj)

    for i, di in enumerate(d, start=1):
        if di == inf:
            print(i, -1)
        else:
            print(i, di)

def bfs(n, Adj):
    d = [inf] * n
    d[0] = 0
    nxts = deque([0])

    while nxts:
        u = nxts.popleft()

        for v in Adj[u]:
            if d[v] == inf:
                d[v] = d[u] + 1
                nxts.append(v)

    return d

if __name__ == '__main__':
    solve()

Python: def bfs(adj, s):
    n = len(adj)
    d = [-1 for _ in range(n)]
    c = [0 for _ in range(n)]

    d[s] = 0
    c[s] = 1

    queue = [s]

    while len(queue) > 0:
        u = queue.pop(0)
        for v in adj[u]:
            if c[v] == 0:
                c[v] = 1
                d[v] = d[u] + 1
                queue.append(v)

    return d


n = int(input())
adj = [[] for _ in range(n)]
for _ in range(n):
    s = [int(x) for x in input().split()]
    u = s[0]
    for v in s[2:]:
        adj[u - 1].append(v - 1)

d = bfs(adj, 0)

for i in range(n):
    print(str(i + 1) + " " + str(d[i]))

Python: #!/usr/bin/env python
# -*- coding: utf-8 -*-
#
# FileName: 	breadth_first_search
# CreatedDate:  2020-04-14 23:40:14 +0900
# LastModified: 2020-04-15 00:14:09 +0900
#


import os
import sys
from collections import deque

def bfs(matrix,n):
    s=0
    color=[0]*n
    color[s]=1
    Q=deque()
    Q.append(s)
    distance = [-1]*n
    distance[0]=0
    while Q:
        u = Q.popleft()
        for v in matrix[u]:
            if color[v]==0:
#                print("{}->{}".format(u,v))
                distance[v]=distance[u]+1
                color[v]=1
                Q.append(v)
        color[u]=2
    
    return distance

def main():
    n=int(input())
    matrix = [[] for _ in range(n)]
    for i in range(n):
        lined = map(int,input().split())
#        print(lined)
        for j,pon in enumerate(lined):
            if j>=2:
                matrix[i].append(pon-1)
#    print(matrix)
    distance = bfs(matrix,n)
    for i,di in enumerate(distance):
        print("{} {}".format(i+1,di))

if __name__ == "__main__":
    main()

Python: n = int(input())
a = [101] * n
a[0] = 0
for i in range(n):
    t = list(map(int, input().split()))
    del t[1]
    if len(t) >= 2:
        for j in range(1, len(t)):
            a[t[j] - 1] = min(a[t[j] - 1], a[t[0] - 1] + 1)
for i in range(n):
    if a[i] == 101:
        print("{} {}".format(i + 1, -1))
    else:
        print("{} {}".format(i + 1, a[i]))

Python: from collections import deque

n = int(input())
graph = [[] for _ in range(n)]
for i in range(n):
    graph[i] += list(map(lambda x: x - 1, list(map(int, input().split()))[2:]))

visited = [-1] * n
que = deque()
# 頂点0を入れておく
que.append(0)
visited[0] = 0
cnt = 0

while que:
    v = que.popleft()
    for nv in graph[v]:
        if not visited[nv] == -1:
            continue
        visited[nv] = visited[v] + 1
        que.append(nv)

for v, d in enumerate(visited, 1):
    print(v, d)