Does Ruby have containers like stacks, queues, linked-lists, maps, or sets?

I checked several Ruby tutorials online and they seemed to use array for everything. So how could I implement the following data structures in Ruby?

• Stacks
• Queues
• Linked lists
• Maps
• Sets

(Moved from Comment)

Well, an array can be a stack or queue by limiting yourself to stack or queue methods (push, pop, shift, unshift). Using push / pop gives LIFO(last in first out) behavior (stack), while using push / shift or unshift / pop gives FIFO behavior (queue).

Maps are http://www.ruby-doc.org/core/classes/Hash.html">hashes</a>;, and a http://ruby-doc.org/stdlib/libdoc/set/rdoc/index.html">Set</a> class already exists.

You could implement a linked list using classes, but arrays will give linked-list like behavior using the standard array methods.

I guess most of it is covered in above answers but just for summing it up for a better explanation:

Stack:

stack = []
stack << 2 # push 2 => stack = [2]
stack << 3 # push 3 => stack = [2, 3]
stack.pop  # pop => 3, stack = [2]

Queue:

# we have a Queue class
queue = Queue.new
queue << 2 # push 2 => queue = [2]
queue << 3 # push 3 => queue = [2, 3] (just a representation, it will be an object though)
queue.pop # pop 2

Linked List:

# A very simple representation
class Node
  attr_accessor :value, :next_node

  def initialize(value, next_node=nil)
	@value = value
	@next_node = next_node
  end
end

class LinkedList

  def initialize(value)
	@head = Node.new(value)
  end

  def add(value)
	current = @head
	while !current.next_node.nil?
	  current = current.next_node
	end
	current.next_node = Node.new(value)
  end
end

ll = LinkedList.new
ll.add(10)
ll.add(20)

Maps:

# Hash incase of ruby
a = {} (or a = Hash.new)
a['one'] = 1 # a = {"one"=>1}
a['two'] = 2 # a = {"one"=>1, "two"=>2}

Set:

# we have a Set class
require 'set'
s = Set.new         # <Set: {}>
s.add(1)            # <Set: {1}>
s.add(2)            # <Set: {1, 2}>
s.add(1)            # <Set: {1, 2}>
s.instance_of?(Set) # true

Yes, although not expressly in name. The Array class can be used as a stack, queue, or linked list. For example, push and pop make it behave like a stack. Ruby's Map is the Hash class. Ruby also has a Set class, although you have to import a module to use it (require 'set').

The Ruby language actually has a Queue class which can be used as .... wait for it... a Queue ;)

It is thread safe and easy to use.

The rest of @James answer is great and accurate.

Heaps/ Priority Queue A min heap/priority queue functionality can be achieved using sorted set.

Creation(Adding data to heap/PQ)

pq = SortedSet.new([3]) #=> #<SortedSet: {3}>
pq.add(1) #=> #<SortedSet: {1, 3}>
pq.add(6) #=> #<SortedSet: {1, 3, 6}>

Deletion(top priority element)

top = pq.first #1
pq.delete(top) #=> #<SortedSet: {3, 6}>, top is '1'
top = pq.first #3
pq.delete(top) #=> #<SortedSet: {6}>

I would like to add Deque implementation (which is more generic in linear DS usage) in Ruby :

class Node
  attr_accessor :value, :next, :prev
  def initialize(value, next_node, prev_node)
    @value = value
    @next = next_node
    @prev = prev_node
  end
end


class Deque
  attr_accessor :start, :end
  def initialize
    @start = @end = nil
  end

  def push_back(val)
    if @start.nil?
      @start = @end = Node.new(val, nil, nil)
    else
      @end.next = Node.new(val, nil, @end)
      @end.next.prev = @end
      @end = @end.next
    end
  end

  def pop_back
    if @start == @end #only one node
      @start = @end = nil
    else
      @end = @end.prev
      @end.next = nil
    end
  end

  def push_front(val)
    @start.prev = Node.new(val, @start, nil)
    @start = @start.prev
  end

  def pop_front
    if @start == @end #only one node
      @start = @end = nil
    else
      @start = @start.next
      @start.prev.next = nil
      @start.prev = nil
    end
  end

  def empty?
    @start.nil? && @end.nil?
  end

  def front
    @start.value unless self.empty?
  end

  def back
    @end.value unless self.empty?
  end

  def print(node)
    arr = []
    while node
      arr << node.value
      node = node.next
    end
    p arr
  end
end


q = Deque.new
q.push_back(1)
q.push_back(2)
q.push_back(3)
q.push_back(4)
q.print(q.start)
q.push_front(0)
q.push_front(-1)
q.print(q.start)
q.pop_back()
q.pop_back()
q.print(q.start)
q.pop_front()
q.pop_front()
q.print(q.start)
p q.front
p q.back

Output :

[1, 2, 3, 4]
[-1, 0, 1, 2, 3, 4]
[-1, 0, 1, 2]
[1, 2]
1
2