Problem:
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Breadth First Search

Write a program which reads an directed graph $G = (V, E)$, and finds the shortest distance from vertex $1$ to each vertex (the number of edges in the shortest path). Vertices are identified by IDs $1, 2, ... n$.

Input

In the first line, an integer $n$ denoting the number of vertices, is given. In the next $n$ lines, adjacent lists of vertex $u$ are given in the following format:

$u$ $k$ $v_1$ $v_2$ ... $v_k$

$u$ is ID of the vertex and $k$ denotes its degree.$v_i$ are IDs of vertices adjacent to $u$.

Constraints

$1 \leq n \leq 100$

Output

For each vertex $u$, print $id$ and $d$ in a line. $id$ is ID of vertex $u$ and $d$ is the distance from vertex $1$ to vertex $u$. If there are no path from vertex $1$ to vertex $u$, print -1 as the shortest distance. Print in order of IDs.

Sample Input 1

4
1 2 2 4
2 1 4
3 0
4 1 3

Sample Output 1

1 0
2 1
3 2
4 1

Reference

Introduction to Algorithms, Thomas H. Cormen, Charles E. Leiserson, Ronald L. Rivest, and Clifford Stein. The MIT Press.

Solution in C# (judge verdict: Accepted)

using System;
using System.Collections.Generic;

namespace ConsoleApp1
{

    class Program
    {
        class Node {
            internal bool visted;
            internal List<int> adj;
            internal int d, f;
            public Node() {
                d = f = 0;
                adj = new List<int>();
                visted = false;
                
            }
        }
        static void Main()
        {
            int n = int.Parse(Console.ReadLine());
            Node[] nodes = new Node[n + 1];
            for (int i = 0; i < n; i++)
            {
                int[] temp = Array.ConvertAll(Console.ReadLine().Split(' '), int.Parse);
                nodes[temp[0]] = new Node();
                for (int k = 0; k < temp[1]; k++)
                {
                    nodes[temp[0]].adj.Add(temp[k + 2]);
                }
            }
            for (int i = 1; i <= n; i++)
                BFS(nodes, i);

            for (int i = 1; i <= n; i++)
                Console.WriteLine(i + " " + nodes[i].d);

        }

        static void BFS(Node[] nodes, int pos) {
            Queue<int[]> q = new Queue<int[]>();
            HashSet<int> visted = new HashSet<int>();
            q.Enqueue(new int[2]{ 1, 0});
            while (q.Count > 0) {
                int[] curr = q.Dequeue();
                visted.Add(curr[0]);
                if (curr[0] == pos)
                {
                    nodes[pos].d = curr[1];
                    return;
                }
                for (int i = 0; i < nodes[curr[0]].adj.Count; i++)
                    if(!visted.Contains(nodes[curr[0]].adj[i])) q.Enqueue(new int[2] { nodes[curr[0]].adj[i], curr[1] + 1 });
            }

            nodes[pos].d = -1;
        }
		
    }
}