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: import abc


class AdjacentGraph:
    """Implementation adjacency-list Graph.
    Beware ids are between 1 and size.
    """
    def __init__(self, size):
        self.size = size
        self._nodes = [[0] * (size+1) for _ in range(size+1)]

    def set_adj_node(self, id_, adj_id):
        self._nodes[id_][adj_id] = 1

    def __iter__(self):
        self._id = 0
        return self

    def __next__(self):
        if self._id < self.size:
            self._id += 1
            return (self._id, self._nodes[self._id][1:])

        raise StopIteration()

    def dfs(self, handler=None):
        def find_first():
            try:
                return visited.index(0) + 1
            except ValueError:
                return None

        visited = [0] * self.size
        first = 1
        while first is not None:
            stack = [(first, 0, 0)]
            while len(stack) > 0:
                i, depth, j = stack.pop()
                if j == 0:
                    if handler:
                        handler.visit(i, depth)
                    visited[i-1] = 1
                    yield i
                try:
                    j = self._nodes[i].index(1, j+1)
                    stack.append((i, depth, j))
                    if visited[j-1] == 0:
                        stack.append((j, depth+1, 0))
                except ValueError:
                    if handler:
                        handler.leave(i)
            first = find_first()

    def bfs(self, handler=None):
        def find_first():
            try:
                return visited.index(0) + 1
            except ValueError:
                return None

        visited = [0] * self.size
        first = 1
        while first is not None:
            queue = [(first, 0)]
            while len(queue) > 0:
                (i, depth), *queue = queue
                if visited[i-1] == 0:
                    if handler:
                        handler.visit(i, depth)
                    visited[i-1] = 1
                    yield i
                    try:
                        j = 0
                        while j < self.size:
                            j = self._nodes[i].index(1, j+1)
                            if visited[j-1] == 0:
                                queue.append((j, depth+1))
                    except ValueError:
                        pass
                if handler:
                    handler.leave(i)
            first = find_first()


class EventHandler(abc.ABC):
    @abc.abstractmethod
    def visit(self, i, depth):
        pass

    @abc.abstractmethod
    def leave(self, i):
        pass


class Logger(EventHandler):
    def __init__(self, n):
        self.log = [(0, 0)] * n
        self.step = 0

    def visit(self, i, depth):
        self.step += 1
        self.log[i-1] = (self.step, depth, 0)

    def leave(self, i):
        self.step += 1
        self.log[i-1] = (self.log[i-1][0], self.log[i-1][1], self.step)

    def by_node(self):
        i = 1
        for discover, depth, finish in self.log:
            yield (i, discover, depth, finish)
            i += 1

def run():
    n = int(input())
    g = AdjacentGraph(n)
    log = Logger(n)

    for i in range(n):
        id_, c, *links = [int(x) for x in input().split()]
        for n in links:
            g.set_adj_node(id_, n)

    for i in g.bfs(log):
        pass

    reachable = None
    for node in log.by_node():
        id_, find, dep, exit = node
        if id_ > 1 and dep == 0:
            reachable = find - 1

        if reachable is not None and find > reachable:
            dep = -1

        print("{} {}".format(id_, dep))


if __name__ == '__main__':
    run()

Python: #=============================================================================
# Breadth First Search
#=============================================================================
import queue

N=int(input())
Graph=[[] for _ in range(N+1)]
dist=[-1 for _ in range(N+1)]
for i in range(1,N+1):
    Graph[i]=list(map(int,input().split()))[2:]


que=queue.Queue()
que.put(1)
dist[1]=0
while not que.empty():
    v=que.get()
    for nv in Graph[v]:
        if dist[nv] != -1:
            continue
        dist[nv]=dist[v]+1
        que.put(nv)
for i in range(1,N+1):
    print(i,dist[i],sep=" ")

Python: from sys import stdin

X = [ 0 for i in range(100) ]
d = [ 0 for i in range(100) ]
G = [[ 0 for i in range(100) ] for i in range(100)]
queue = [ 0 for i in range(100) ]

t = 0
head = 0
tail = 0

def BFS(i) :
	global head
	for j in range(n) :
		if G[i][j] == 1 and d[j] == 0 :
			d[j] = d[i] + 1
			queue[head] = j
			head += 1

def tailQ() :
	global tail
	tail += 1
	return queue[tail-1]


n = int(input())
for i in range(n) :
	X[i] = stdin.readline().strip().split()


for i in range(n) :
	for j in range(int(X[i][1])) :
		G[int(X[i][0])-1][int(X[i][j+2])-1] = 1

BFS(0)
while head-tail != 0 : 
	BFS(tailQ())

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

Python: from collections import deque

n = int(input())
G = []
G.append([])
for i in range(n):
    v = list(map(int, input().split()))
    G.append(v[2:])

checked = [False for i in range(n + 1)]
d = [-1 for i in range(n + 1)]

q = deque()
q.append(1)
checked[1] = True
d[1] = 0

while q:
    current = q.pop()
    for adj in G[current]:
        if not checked[adj]:
            q.append(adj)
            checked[adj] = True
            d[adj] = d[current] + 1

for id in range(1, n + 1):
    print(id, d[id])