Finished example

lines.rb

class Line
  attr_accessor :startpoint
  attr_accessor :endpoint

  def initialize(startpoint, endpoint)
    @startpoint = startpoint
    @endpoint = endpoint
  end

  def to_s
    "(#{@startpoint}, #{@endpoint})"
  end
end


# Return an array of merged Lines
# 
def merge_lines(lines)
  current_line = nil
  merged_lines = []
  
  # (1, 5), (2, 6), (6, 10), (15, 20), (17, 21)
  # (1, 10), (15, 21)
  lines.each_with_index do |line, index|
    
    # line (1, 10)
    if current_line.nil?
      current_line = Line.new(line.startpoint, line.endpoint)
    
    else
      # current_line = (15, 21)
      # line
      # 
      if line.endpoint > current_line.endpoint
        endpoint = line.endpoint
        current_line = Line.new(current_line.startpoint, endpoint)
      end
    end
    
    # 15, 21
    next_line = lines[index+1]
    
    if next_line
      if next_line.startpoint > current_line.endpoint
        merged_lines << current_line
        current_line = nil
      end
    else
      merged_lines << current_line
    end
  end
  
  pp merged_lines
  merged_lines
end

example1 = [
  Line.new(1, 5),
  Line.new(2, 6),
  Line.new(6, 10),
  Line.new(15, 20),
  Line.new(17, 21)
]

example2 = [
  Line.new(1, 10),
  Line.new(15, 21)
]

example3 = [
  Line.new(1, 5),
  Line.new(2, 3),
  Line.new(4, 8),
  Line.new(8, 10)
]

merge_lines(example1)
merge_lines(example2)
merge_lines(example3)