nikasulo

class Node
  attr_accessor :value, :next_node, :prev_node

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

nikasulo

class Deque
  def initialize
    @first = Node.new(nil)
    @last = @first
  end
end

nikasulo

def pushFront(number)
  @first = Node.new(number, @first, nil)
  @last = @first if @last and @last.value.nil?
end
  

nikasulo

def pushBack(number)
  self.pushFront(number) && return if @first.value.nil?
  @last.next_node = Node.new(number)
  @last = @last.next_node
end

nikasulo

def popFront
  if @last == @first
    @first = Node.new(nil)
    @last = @first
    return 
  end
  @first = @first.next_node
end

nikasulo

def popBack
  @last = @last.prev_node and return unless @first == @last
  @first = Node.new(nil)
  @last = @first
end

nikasulo

def topFront
  @first.value unless @first.nil?
end

nikasulo

def topBack
  @last.value unless @last.nil?
end

nikasulo

def is_empty?
  @first.nil?
end

nikasulo

def sliding_maximum(k, array)
    res = []
    for i in 0..array.length - k do
        max = array[i]
        for j in i...i+k do 
            max = array[j] > max ? array[j] : max
        end 
        res << max
    end   
    res