Let’s Party with Stacks and Queues! Pt 1

I have consumed several excellent written/video tutorials on Stacks and Queues, with their characteristics and limitations. However, I haven’t seen many examples where these 2 data structures are implemented beyond defining their class and associated methods.
So I’ve created a Ruby tutorial that implements stacks and queues within an example where meals are served to a line of guests at a party!
In this tutorial, we will create a short program that takes two arrays (Stack of Meals, and Queue of Guests) and advances the queue based on whether the top meal matches the culinary preferences of the first guest in the queue.
Sound like fun? Let’s dive in!
Let’s build the MealStack class first. This class will accept an array of meals (meals_array) identified by their type (such as ‘vegetarian’, ‘regular’, ‘vegan’).
class Stack
attr_accessor :meals

def initialize(meals_array)
self.meals = meals_array
end
end

We want to be able to do the following with a MealStack:

See what meal is at the top of the stack (top_meal), which is the last item in the array:

def top_meal
meals.last
end

Take the top meal off the stack (take_meal):

def take_meal
meals.pop
end

Know if all meals are gone (stack_empty?):

def stack_empty?
meals.empty?
end

View all remaining meals in the stack (display_meals). We call .reverse on self.plates so that the last array entry appears first (as the top of the stack):

def display_meals
meals.reverse.inspect
end

Know how many meals are in the stack (size):

def size
meals.length
end

Here is the complete MealStack class:
class MealStack
attr_accessor :meals

def initialize(meals_array)
meals = meals_array
end

def top_meal
meals.last
end

def take_meal
meals.pop
end

def stack_empty?
meals.empty?
end

def display_meals
meals.reverse.inspect
end

def size
meals.length
end
end

Now let’s build the GuestQueue class, which accepts an array of guests identified by their meal preference. For simplicity’s sake, guests’ meal preferences are identified same as the meals array – ‘vegetarian’, ‘vegan’, etc.
class GuestQueue
attr_accessor :guests

def initialize(guest_array)
self.guests = guest_array
end
end

We want to be able to do the following with a QueueStack:

Know who is at the front of the queue (first_guest):

def first_guest
guests.first
end

Have guests able to join the queue (join_queue(guest)):

def join_queue(guest)
guests.push(guest)
end

Have guests able to leave the queue (leave_queue):

def leave_queue
guests.shift
end

Have guests able to rejoin the queue (rejoin_queue):

def rejoin_queue
join_queue(self.leave_queue)
end

Know if all guests have been served (queue_empty?):

def queue_empty?
guests.empty?
end

View all remaining guests in the queue (display_queue):

def display_queue
guests.inspect
end

Know how many guests are in the queue (size):

def size
guests.length
end

Here is the complete GuestQueue class:
class GuestQueue
attr_accessor :guests

def initialize(guest_array)
self.guests = guest_array
end

def first_guest
guests.first
end

def join_queue(guest)
guests.push(guest)
end

def leave_queue
guests.shift
end

def rejoin_queue
join_queue(leave_queue)
end

def queue_empty?
guests.empty?
end

def display_queue
guests.inspect
end

def size
guests.length
end
end

Finally, let’s make sure our MealStack and GuestQueue classes work:
my_meals = MealStack.new(%w[vegetarian vegan normal paleo vegan normal paleo])

puts my_meals.size # 7
puts my_meals.top_meal # paleo
puts my_meals.take_meal # paleo
puts my_meals.stack_empty? # false
puts my_meals.take_meal # normal
puts my_meals.take_meal # vegan
puts my_meals.size # 4

– – –

my_friends = GuestQueue.new(%w[normal paleo vegan vegetarian vegan normal paleo])

puts my_friends.size # 7
puts my_friends.first_guest # normal
puts my_friends.leave_queue # normal
puts my_friends.leave_queue # paleo
puts my_friends.size # 5
puts my_friends.rejoin_queue # vegan
puts my_friends.leave_queue # vegetarian
puts my_friends.first_guest # vegan

In the next part, things get interesting when we build our Party class!

Link: https://dev.to/msarit/let-s-party-with-stacks-and-queues-pt-1-35g