グラフアルゴリズム - 幅優先探索

# Queue
class Array
  alias_method :enqueue, :push
  alias_method :dequeue, :shift
end
 
# u : Index of nodes starting from 1...N
# k : degree of this node
# v : array of vertices connected with this node
# c : :white(=undiscovered), :gray(=frontier), :black(finished searching)
# d : distance when the vertex is first discovered
# pi: predecessor vertex
Node = Struct.new(:u, :k, :v, :c, :d, :pi)
 
class Graph
 
  attr :nodes, true
 
  def initialize(n)
    @nodes = Array.new(n){ Node.new }
  end
 
  def add_graph_node(u, v, d = 0)
    @nodes[u-1].u = u
    if not v.nil?
      (@nodes[u-1].v ||= []).push(v)
      @nodes[u-1].k = @nodes[u-1].v.length ||= 0
    else
      @nodes[u-1].v = [] if @nodes[u-1].v.nil?
      @nodes[u-1].k = 0
    end
    @nodes[u-1].c = :white
    @nodes[u-1].d = d
    @nodes[u-1].pi = nil
  end
 
  def reset()
    @nodes.each do |node|
      node.c  = :white
      node.d  = -1
      node.pi = nil
    end
  end
 
  def dist()
    puts "d : #{@nodes.map{|node| node.d}.to_a.to_s}"
    puts "pi: #{@nodes.map{|node| node.pi}.to_a.to_s}"
  end
 
  def bfs(start, queue)
 
    start_idx = (start - 1).to_i
    @nodes[start_idx].c  = :gray
    @nodes[start_idx].d  = 0
    @nodes[start_idx].pi = nil
    queue.enqueue(@nodes[start_idx])
 
    while not queue.empty?
 
      u = queue.dequeue
      break if u.v.nil?
 
      u.v.each do |label|
        v = @nodes[label-1]
        if v.c == :white
          v.c  = :gray
          v.d  = u.d.to_i + 1
          v.pi = u
          queue.enqueue(v)
        end
      end
      u.c = :black
    end
  end
end
 
# start
lines = $stdin.read
array = lines.split("\n")
 
N     = array[0].to_i
graph = Graph.new(N)
 
for i in 1...N+1
  seps = array[i].split(" ")
  u    = seps.drop(0)[0].to_i
  k    = seps.drop(1)[0].to_i
  vs   = seps.drop(2).map(&:to_i)
  #puts "add_graph_node(#{u} <--> #{v})"
  for v in vs
    graph.add_graph_node(u, v)
  end
  graph.add_graph_node(u, nil) if vs.length == 0
end
 
graph.bfs(1, [])
 
graph.nodes.each_with_index do |elem, idx|
    puts "#{idx+1} #{graph.nodes[idx].d.to_i}"
end