组合数组并保留顺序 - 但优先考虑一个数组的顺序而不是另一个

Posted 2023-03-15

【中文标题】组合数组并保留顺序 - 但优先考虑一个数组的顺序而不是另一个

【英文标题】：Combine arrays and preserve ordering - but prioritize one array's ordering over another

【发布时间】：2016-08-15 00:41:25

【问题描述】：

假设我有两个数组：

Arr1 = ["1-a", "1-b", "1-c"]
Arr2 = ["2-a", "2-b", "2-c"]

我知道如何将它们组合成一个数组，保持它们的顺序：

  Arr1.zip(Arr2).flatten(1)
  # => ["1-a", "2-a", "1-b", "2-b", "1-c", "2-c"]

在本例中，我认为 Arr1 的“优先级”高于 Arr2，因为“1-a”出现在“2-a”之前，“1-c”出现在“2-c”之前。

如果 Arr2 被“优先化”，会发生以下情况：

Arr2.zip(Arr1).flatten(1)
# => ["2-a", "1-a", "2-b", "1-b", "2-c", "1-c"]

在这些示例中，“优先级”是一种二元状态。但是如果我想使用小数呢？这就是我想要发生的事情：

y axis: percentage of added nodes that are Arr1
x axis: percent completion of Arr2 iteration

   100% |                     X
        |           
   75%  |                X
        |
   50%  |           X
        |
   25%  |       X
        |
    0%  |  X        
        ------------------------- 
           0%  25%  50%  75%  100%

【参考方案1】：

这是我写的

class Array

  # helper method to help with testing
  def mean
    map(&:to_f).reduce(&:+) / length.to_f
  end

  # target is another array
  # priority is a number between 0 and 1
  #   if 0, then target will not be merged in at all
  #   if 1, then the result will be ~50% composed of target
  # returns array with the same length as self
  # Note that the result will not contain all of self.concat(target)

  def priority_merge(priority, target)
    # clone the arrays to avoid side-effects
    arr1, arr2 = [self, target].map(&:clone)
    # get the original length to determine the results length
    arr1_len = arr1.length.to_f
    # convert priority to float
    priority = priority.to_f
    # initialize a results set
    results = []
    # populate the results set
    arr1_len.to_i.times do |arr1_idx|
      # determine the percentage completed through iteration
      pct_iterated = arr1_idx.to_f / arr1_len.to_f
      # calculate per-run likelihood of favoring target
      per_run_priority = pct_iterated * priority
      # conclusively determine which array this iteration will pull from
      num_true_cases = (100.0 * per_run_priority).to_i
      cases = num_true_cases.times.map  true .concat((100 - num_true_cases).times.map  false )
      priority_run_result = cases.sample
      # push from arr2 if the priority run result is true, otherwise push from arr1
      elem_to_push = (priority_run_result ? arr2 : arr1).shift
      # if arr2 is empty, push from arr1 instead 
      results << elem_to_push || arr1.shift
    end
    results
  end
end

并测试它

a1 = 50.times.map  1 
a2 = 50.times.map  2 

puts "MERGE CASE 1"
result = 50.times.map do
  result = a1.priority_merge(1.0, a2)
  result.select  |item| item == 2 .count.to_f / a1.length.to_f
end
puts result.mean
# => is around 50%

puts "MERGE CASE 0.5"
result = 50.times.map do
  result = a1.priority_merge(0.5, a2)
  result.select  |item| item == 2 .count.to_f / a1.length.to_f
end
puts result.mean
# => is around 25%
puts "MERGE CASE 0"
result = 50.times.map do
  result = a1.priority_merge(0.0, a2)
  result.select  |item| item == 2 .count / a1.length.to_f
end
puts result.mean
# => is 0%