重量随机项目 [英] Random item by weight

问题描述

例如我有这样的数据：

headings = { 
         :heading1 => { :weight => 60, :show_count => 0}
         :heading2 => { :weight => 10, :show_count => 0}
         :heading3 => { :weight => 20, :show_count => 0}
         :heading4 => { :weight => 10, :show_count => 0}
       }
total_views = 0

现在我想为每个标题基于其weightages。例如，对于前10个请求/迭代，标题1 ， heading3 ， heading2 和 heading4 将为了分别为6，2，1，1次服完（以重量计）。

Now I want to serve each heading based on their weightages. For instance, for first 10 requests/iterations, heading1, heading3, heading2 and heading4 would be served 6, 2, 1, and 1 times respectively in order (by weight).

有关服务的标题每次迭代show_count将由一个递增并total_views也将在全球范围增加。

For every iteration show_count of served heading will increment by one and total_views will also increment globally.

能否请您提出的算法或者一些红宝石code来处理这个问题。

Could you please suggest an algorithm or some ruby code to handle this.

推荐答案

这要根据你所需要的细节为您的基本情况，并可以修改：

This should work for your basic case and can be modified according to the details of what you need:

 class Heading
   attr_reader :heading, :weight, :show_count

   def initialize(heading,weight=1)
     @heading=heading
     @weight=weight
     @show_count=0
   end

   def serve
     puts "Served #{@heading}! "  
     @show_count += 1
   end
 end

 class HeadingServer
   attr_reader :headings

   def initialize(headings_hash)
     @headings=headings_hash.map {|h, data| Heading.new(h,data[:weight])}
     @total_weight=@headings.inject(0) {|s,h| s+= h.weight}
   end

   def serve(num_to_serve=@total_weight)
     @headings.sort {|a,b| b.weight <=> a.weight}.each do |h| 
       n = (h.weight * num_to_serve) / @total_weight  #possibility of rounding errors
       n.times { h.serve }
     end
   end

   def total_views
     @headings.inject(0) {|s,h| s += h.show_count}
   end
 end

headings = { 
  :heading1 => { :weight => 60, :show_count => 0},
  :heading2 => { :weight => 10, :show_count => 0},
  :heading3 => { :weight => 20, :show_count => 0},
  :heading4 => { :weight => 10, :show_count => 0}
}

# Example Usage:

hs = HeadingServer.new(headings)

hs.serve(10)  

hs.headings.each {|h| puts "#{h.heading} : served #{h.show_count} times"}

puts "Total Views: #{hs.total_views}" 

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