LRU wip

lru.rb

class Node
    attr_accessor :prev, :next, :value 
end
    
class ListManager
    def initialize(capacity)
        @capacity = capacity
        @used=0
        @head = nil
        @last  =nil
    end
    def use_key pos
        #puts "#got here use_key #{pos} #{pos.prev},head is #{@head}"
        return @pos if pos == @head
        if pos == @last
             @last = pos.prev 
        else
             pos.next.prev = pos.prev #if pos.next
        end
        pos.prev.next = pos.next
        pos.prev = nil
        pos.next = @head
        @head.prev=pos
        @head = pos
    end
    def add_key value
         if @used < @capacity
             n = Node.new
             if @head
                 @head.prev = n
                 n.next = @head
             else
                 @last = n
             end
             n.value = value
             @head = n
             @used += 1
            return @head, nil
         else
             evicted_key = @last.value #testme
             pos = use_key @last
             return pos, evicted_key
         end 
    end
end
    
class LRUCache

=begin
    :type capacity: Integer
=end
    def initialize(capacity)
      @dict = {}  #returns value, list_index
      @node = ListManager.new(capacity)
    end


=begin
    :type key: Integer
    :rtype: Integer
=end
    def get(key)
        
       value, pos = @dict[key]
        puts "get #{key} gives #{value}"
       if pos
           @node.use_key pos  
           return value 
       else
           return -1
       end
    end

=begin
    :type key: Integer
    :type value: Integer
    :rtype: Void
=end
    def put(key, value)
        puts "puts #{key}, #{value} #{@dict.keys}"
        lookup = @dict[key]
        if lookup
            ptr = @node.use_key lookup[1]
        else
            
            ptr, evicted_key = @node.add_key(key)
            #puts "evicted #{evicted_key}, dict #@dict"
            @dict.delete(evicted_key) if evicted_key
            
        end    
        @dict[key] = [value,ptr]
    end


end

# Your LRUCache object will be instantiated and called as such:
# obj = LRUCache.new(capacity)
# param_1 = obj.get(key)
# obj.put(key, value)