gistfile1.rb

require 'pp'

class Path < Struct.new(:start_node, :end_node, :color, :type)
  def to_s
    [start_node, end_node, color, type].join(' ')
  end
end


class Test
  def initialize
    @paths = %Q{A B R C
    B E B C
    B C B T
    C D G T}.split("\n").map{|ln|
      Path.new(*ln.split(' '))
    }
    @adjacency_map = {}
  end

  attr_reader :adjacency_map

  def build_adjacency
    @paths.each do |start_path|
        @paths.each do |end_path|
            next if start_path == end_path
            
            # 3 cases for edge adcency
            if (start_path.end_node == end_path.start_node) || (start_path.start_node == end_path.end_node) || (start_path.start_node == end_path.start_node)
                if @adjacency_map.has_key?("#{start_path}".to_s)
                    @adjacency_map[:"#{start_path}".to_s] << end_path
                else
                    value = [end_path]
                    @adjacency_map[:"#{start_path}".to_s] = value
                end
            end
        end
    end
  end
end

t = Test.new
t.build_adjacency

pp t.adjacency_map
# output:
#  {"A B R C"=>
#    [#<struct Path start_node="B", end_node="E", color="B", type="C">,
#     #<struct Path start_node="B", end_node="C", color="B", type="T">],
#   "B E B C"=>
#    [#<struct Path start_node="A", end_node="B", color="R", type="C">,
#     #<struct Path start_node="B", end_node="C", color="B", type="T">],
#   "B C B T"=>
#    [#<struct Path start_node="A", end_node="B", color="R", type="C">,
#     #<struct Path start_node="B", end_node="E", color="B", type="C">,
#     #<struct Path start_node="C", end_node="D", color="G", type="T">],
#   "C D G T"=>[#<struct Path start_node="B", end_node="C", color="B", type="T">]}