the exercise's solution to the problem proposed by Moblox.io

stack_o_1.rb

#Implement in constant time, i.e. O(1), the following operations: push, pop, retrieve the minimum element.
 class Stack 
  attr_accessor :queue
   def initialize 
     @queue = [] 
     @min = [] 
   end

   def push e 
     @queue.push(e) 
     if [email protected]? && @min.min > e 
       @min.shift
     end 
     @min.push e
     self.queue 
   end

   def pop 
     if @queue.first == @min.first 
       @min.shift 
     end 
     @queue.shift 
   end

   def min 
     @min.first 
   end 
end