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)

#include <stdio.h>
#include <stdlib.h>

#define O 0
#define I 1
#define H 100

int n,l,j,u,k,t;
int list[H][H];
int lengthlist[H];

void search(int y, int len){
  int i;
  len++;
  lengthlist[y]=len;
  for(i=O;i<n;i++){
    if(list[y][i]==I){
      if(lengthlist[i] <= len && lengthlist[i] >=O){
        continue;
      }
      search(i,len);
    }
  }
}

int main(){
  scanf("%d",&n);
  for(l=O;l<n;l++){
    scanf("%d",&u);
    scanf("%d",&k);
    for(j=O;j<k;j++){
      scanf("%d",&t);
      list[u-I][t-I]=I;
    }
  }
  for(l=O;l<n;l++){
    lengthlist[l]=-I;
  }
  search(O,-I);
  for(j =O;j<n;j++){
    printf("%d %d\n",j+I,lengthlist[j]);
  }
  return O;
}