Go: package main

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

type AdjacentList struct {
	matrix [][]int
}

func NewEmptyAdjacentList(dim int) *AdjacentList {
	matrix := make([][]int, dim)
	for i := 0; i < dim; i++ {
		matrix[i] = make([]int, dim)
	}
	return &AdjacentList{matrix: matrix}
}

func (al *AdjacentList) set(node int, adjacent int) {
	al.matrix[node-1][adjacent-1] = 1
}

func (al *AdjacentList) findAdjacentsFor(node int) []int {
	adjacents := []int{}
	for i, v := range al.matrix[node-1] {
		if v == 1 {
			adjacents = append(adjacents, i+1)
		}
	}
	return adjacents
}

type DistanceList struct {
	list []int
}

func NewDistanceList(dim int) *DistanceList {
	list := make([]int, dim)
	for i := 0; i < dim; i++ {
		list[i] = -1
	}
	return &DistanceList{list: list}
}

func (dl *DistanceList) set(node int, distance int) {
	dl.list[node-1] = distance
}

func (dl *DistanceList) get(node int) int {
	return dl.list[node-1]
}

func (dl *DistanceList) isVisited(node int) bool {
	return dl.list[node-1] >= 0
}

type Position struct {
	node     int
	distance int
}

func main() {
	sc := bufio.NewScanner(os.Stdin)
	sc.Split(bufio.ScanWords)

	dim, err := nextInt(sc)
	if err != nil {
		panic(err)
	}

	al := NewEmptyAdjacentList(dim)

	for i := 1; i <= dim; i++ {
		node, err := nextInt(sc)
		if err != nil {
			panic(err)
		}

		adjacentNum, err := nextInt(sc)
		if err != nil {
			panic(err)
		}
		for j := 0; j < adjacentNum; j++ {
			adjacent, err := nextInt(sc)
			if err != nil {
				panic(err)
			}
			al.set(node, adjacent)
		}
	}

	dl := NewDistanceList(dim)

	bfs(al, dl)

	for i := 1; i <= dim; i++ {
		fmt.Printf("%d %d\n", i, dl.get(i))
	}
}

func bfs(al *AdjacentList, dl *DistanceList) {
	stack := []Position{Position{node: 1, distance: 0}}
	for len(stack) > 0 {
		currentPosition := stack[0]
		stack = stack[1:]
		if !dl.isVisited(currentPosition.node) {
			dl.set(currentPosition.node, currentPosition.distance)
		}
		for _, v := range al.findAdjacentsFor(currentPosition.node) {
			stack = append(stack, Position{node: v, distance: currentPosition.distance + 1})
		}
	}
}

func nextInt(sc *bufio.Scanner) (int, error) {
	sc.Scan()
	return strconv.Atoi(sc.Text())
}

Python: from collections import deque
import sys


def LI(): return list(map(int, sys.stdin.buffer.readline().split()))
def I(): return int(sys.stdin.buffer.readline())


class Graph:
    def __init__(self, n, is_directed=False):
        """
        :param n: 頂点数
        :param is_directed: 有向グラフ(True)か無向グラフか(False)
        """
        self.n = n
        self.graph = [[] for _ in range(n)]
        self.is_directed = is_directed

    def add_edge(self, u, v):
        """uからvへの(有向な)辺をつなぐ"""
        self.graph[u].append(v)
        if not self.is_directed:
            self.graph[v].append(u)

    def search(self, start, mode):
        '''開始地点から各頂点まで幅/深さ優先探索を行って得られた距離のリストを返す
        Args:
          start(int): 開始地点となる頂点
          mode(str): 幅優先探索(b)か深さ優先探索(d)を指定

        Returns:
          List[int]: 開始地点からの距離(未到達の場合は-1)
        '''
        dists = [-1] * self.n
        que = deque([start])
        dists[start] = 0
        if mode == 'b':
            get_v = que.popleft
        else:
            get_v = que.pop
        while que:
            now_v = get_v()
            for next_v in self.graph[now_v]:
                if dists[next_v] != -1:
                    continue
                que.append(next_v)
                dists[next_v] = dists[now_v] + 1
        return dists


n = I()
g = Graph(n, is_directed=True)
for _ in range(n):
    u, k, *v = LI()
    u -= 1
    if v == []:
        continue
    for vi in v:
        vi -= 1
        g.add_edge(u, vi)
res = g.search(0, 'b')
for i in range(n):
    print(i + 1, res[i])

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]))