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;

struct G {

    public int edge, d;
    public int[] a;

    public G(int n) {
        edge = n;
        a = new int[n];
        d = -1;
    }
}

class C11{
    public static void Main() {

        int n = int.Parse(Console.ReadLine());
        G[] g = new G[n + 1];

        for(int i = 0; i < n; i++) {
            string[] str = Console.ReadLine().Split(' ');
            int stringToInt1 = int.Parse(str[0]), stringToInt2 = int.Parse(str[1]);
            g[stringToInt1] = new G(stringToInt2);

            for(int j = 0; j < stringToInt2; j++) {
                g[stringToInt1].a[j] = int.Parse(str[j + 2]);
            }
        }

        g[1].d = 0;
        var queue = new Queue<int>();
        queue.Enqueue(1);

        while(queue.Count > 0) {
            int id = queue.Dequeue();

            for(int i = 0; i < g[id].edge; i++) {
                if(g[g[id].a[i]].d == -1) {
                    g[g[id].a[i]].d = g[id].d + 1;
                    queue.Enqueue(g[id].a[i]);
                }
            }
        }

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

    }
}