bst.rb

class Node
  attr_accessor *%i(value left right)
  def initialize(value, left: nil, right: nil)
    self.value = value
    self.left = left
    self.right = right
  end
end

def root
  nodes = (1..9).map{|i| Node.new(i)}

  # Leaves
  nodes[1].left = nodes[0]
  nodes[1].right = nodes[2]
  nodes[7].left = nodes[6]
  nodes[7].right = nodes[8]

  nodes[3].left = nodes[1]
  nodes[5].right = nodes[7]

  nodes[4].left = nodes[3]
  nodes[4].right = nodes[5]

  nodes[4]
end

def find_min(root)
  # Your code here
end

def find_nth_min(root, n)
  # Your code here
end