架构师第一期作业（第 8 周）

# 单向链表节点定义
class Node
  attr_accessor :data, :next
  def initialize(data, next_node = nil)
    @data = data
    @next = next_node
  end
end
# 模拟堆栈结构
class Stack
  def initialize
    @array = []
  end
  def length
    @array.length
  end
  def push item
    @array << item
  end
  def pop
    @array.shift
  end
end
def find_merge_node head1, head2
  stack1 = Stack.new
  stack2 = Stack.new
  while head1 != null
    stack1.push head1
    head1 = head1.next
  end
  while head2 != null
    stack2.push head2
    head2 = head2.next
  end
  result = nil
  while stack1.length > 0 && stack2.length > 0
    node1 = stack1.pop
    node2 = stack2.pop
    break if node1.data != node2.data
    result = node1
  end
  result
end