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 JAVA (judge verdict: Time Limit Exceeded)

import java.util.ArrayList;
import java.util.LinkedList;
import java.util.Scanner;

public class Main {
	
	Scanner sc = new Scanner(System.in);
	LinkedList<Integer> array = new LinkedList<Integer>();
	public void run() {
			int n = sc.nextInt();
		calc(n);
	}
	
	public void calc(int n){
		int[][] gyouretsu = new int[n][n];
		for(int i = 0; i < n; i++){
			for(int j = 0; j < n; j++){
				gyouretsu[i][j] = 0;
			}
		}
		for(int i = 0; i < n; i++){
			int u = sc.nextInt();
			int k = sc.nextInt();
			for(int j = 0; j < k; j++){
				int v = sc.nextInt();
				gyouretsu[u-1][v-1] = 1;
			}
		}
		int[] ans = new int[n];
		for(int i = 0; i < n; i++){
			ans[i] = -1;
		}
		array.push(0);
		rec(gyouretsu, 0, ans);
	
		for(int i = 0; i < n; i++){
			System.out.println(i+1 + " " + ans[i]);
		}
	}
	public void rec(int[][] gyouretsu, int t, int[] ans){
		int s = array.size();
		for(int i = 0; i < s; i++){
			int now = array.get(i);
			ans[now] = t;
		}
		for(int i = 0; i < s; i++){
			int now = array.get(0);
			array.remove(0);
			for(int j =0; j <  gyouretsu[now].length; j++){
				if(gyouretsu[now][j] == 1 && ans[j] == -1){
					array.add(j);
				}
			}
		}
		if(array.size() != 0){
		rec(gyouretsu, t+1, ans);
		}
	}

	public static void main(String[] args) {
		new Main().run();
	}
}