Implementation of Floyd's Cycle Detection Algorithm

scratch.rb

class Node
  attr_reader :value
  attr_accessor :next_node

  def initialize(value, next_node = nil)
    @value = value
    @next_node = next_node
  end
  
  def end?
    next_node.nil?
  end
  
  def ==(node)
    node.value == value
  end
end

class Floyd
  def initialize(node)
    @tortoise = node
    @hare = node
  end

  def cycle?
    loop do
      return if @hare.end?
      @hare = @hare.next_node
      return if @hare.end?
      @hare = @hare.next_node
      @tortoise = @tortoise.next_node
      return true if @hare == @tortoise
    end
  end
end

# Linked List #3: (optional) Floyd's Cycle Detection Algorithm
n1 = Node.new(1, Node.new(2, Node.new(3)))
puts "List 1: #{Floyd.new(n1).cycle? ? "Has cycle" : "No cycle"}"

looped1 = Node.new 1
looped2 = Node.new 2
looped3 = Node.new 3
looped1.next_node = looped2
looped2.next_node = looped3
looped3.next_node = looped1
puts "List 2: #{Floyd.new(looped3).cycle? ? "Has cycle" : "No cycle"}"

Output:

[Running] ruby "/Users/diego/Desktop/scratch.rb"
List 1: No cycle
List 2: Has cycle

[Done] exited with code=0 in 0.039 seconds