Strongly connected components solution

gistfile1.txt

class Lecture04
  attr_accessor :graph_reverse, :explored, :number_nodes_processed, :current_source_vertex, :finishing_times, :leaders, :new_graph, :directory

  def initialize(dir)
    @directory = dir
    @graph_reverse = {}
    File.foreach(@directory) do |line|
      current_edge = line.strip.split.reverse.map(&:to_i)
      @graph_reverse[current_edge[0].to_s] = [] if @graph_reverse[current_edge[0].to_s].nil?
      @graph_reverse[current_edge[0].to_s] << current_edge[1]
    end;nil

    @new_graph       = {}
    @explored        = []
    @finishing_times = []
    @leaders         = []

    @number_nodes_processed = 0
    @current_source_vertex  = nil
  end
  
  def generate_new_graph
    File.foreach(@directory) do |line|
      current_edge = line.strip.split.map(&:to_i)
      new_tail_vertex = @finishing_times[current_edge[0]-1]
      @new_graph[new_tail_vertex.to_s] = [] if @new_graph[new_tail_vertex.to_s].nil?
      @new_graph[new_tail_vertex.to_s] << @finishing_times[current_edge[1]-1]
    end;nil
  end

  def dfs_loop(number_of_vertices)
    number_of_vertices.downto(1) do |vertex|
      unless @explored[vertex-1]
        @current_source_vertex = vertex
        dfs(vertex)
      end
    end
  end

  def dfs(vertex)
    @explored[vertex-1] = true
    unless @graph_reverse[vertex.to_s].nil?
      @graph_reverse[vertex.to_s].each do |v|
        dfs(v) unless @explored[v-1]
      end
    end

    @number_nodes_processed += 1
    @finishing_times[vertex-1] = @number_nodes_processed
  end

  def dfs_loop_2nd_pass(number_of_vertices)
    @explored = []
    @current_source_vertex = nil
    number_of_vertices.downto(1) do |vertex|
      unless @explored[vertex-1]
        @current_source_vertex = vertex
        dfs_2nd_pass(vertex)
      end
    end
  end
  
  def dfs_2nd_pass(vertex)
    @explored[vertex-1] = true
    @leaders[vertex-1] = @current_source_vertex
    unless @new_graph[vertex.to_s].nil?
      @new_graph[vertex.to_s].each do |v|
        dfs_2nd_pass(v) unless @explored[v-1]
      end
    end
  end
end

directory = ''
lecture = Lecture04.new directory
lecture.dfs_loop 875714
lecture.generate_new_graph
lecture.dfs_loop_2nd_pass 875714

answer = lecture.leaders.group_by {|x| x}.values.map(&:count).sort.reverse.take(5).inspect

puts answer