garden.rb

require 'active_support/core_ext/array'

class Garden
  attr_reader :layout, :grouped_by_student, :students

  def initialize(layout, students = Garden.default_students)
    @students = students
    @layout = Garden.parse(layout)
    @grouped_by_student = group_by_student
    define_student_lookups
  end

  def define_student_lookups
    students.sort.each_with_index do |name, index|
      instance_eval "def #{name.downcase}; grouped_by_student[#{index}]; end"
    end
  end

  def group_by_student
    Array.new(number_of_students){ [] }.tap do |by_student|
      pods.each_with_index do |pod, index|
        by_student[ index % number_of_students ] += pod
      end
    end
  end

  def number_of_students
    layout.size / flowers_per_student
  end

  def flowers_per_student
    4
  end

  def pods
    layout.in_groups_of(2)
  end

  def self.parse(layout)
    codes = layout.split("").select{|code| code != "\n"}
    codes.collect{|c| Flower.from_code(c)}
  end

  def self.default_students
    %w(Alice Bob Charlie David Eve Fred 
       Ginny Harriet Ileana Joseph
       Kincaid Larry)
  end
end

module Flower
  def self.from_code(code)
    {"V" => :violets,
     "C" => :clover,
     "R" => :radishes,
     "G" => :grass
    }[code]
  end
end