有人可以解释如何注入（Hash.new（0））{|合计，bigram | total [bigram] + = 1;总计} .sort_by {| _key，值|值} .reverse.to_h有效吗？

Question

 alphabet = ["A","B","C","D","E","F","G","H","I","J",
  "K","L","M","N","O","P","Q","R","S","T",
  "U","V","W","X","Y","Z"," ",".",",",";",
  "-","'"
]
file = File.read("vt_00.txt")

i = 0
while i < alphabet.count do
  single_char = alphabet[i]
  single_char_count = file.count(single_char)
  print "#{alphabet[i]} = #{single_char_count} "
  j = 0
  while j < alphabet.count do
    two_chars = alphabet[i] + alphabet[j]  
    two_chars_count = file.scan(two_chars).count
    if two_chars_count > 10 && two_chars_count < 15
      print "#{two_chars} = #{two_chars_count} "
    end
    k = 0
    while k < alphabet.count do
      three_chars = alphabet[i] + alphabet[j] + alphabet[k]
      three_chars_count = file.scan(three_chars).count
      if three_chars_count > 10 && three_chars_count < 15
        print "#{three_chars} = #{three_chars_count} "
      end
      k += 1
    end
    j += 1
  end
  i += 1
end 

我有类似高级代码的代码。但是后来我通过each_cons找到了一个解决方案，您能解释一下它的工作原理吗？我不明白.inject .. part。

count = string.each_cons(1).inject(Hash.new(0)) { |total, bigram| total[bigram] += 1; total }.sort_by {  |_key, value| value }.reverse.to_h

Answer 1

更详细的编写方式为：

total = Hash.new(0)
string.each_cons(1).each{|bigram| total[bigram] += 1} 

inject允许注入一些起始值（Hash.new(0)->我们使用默认值0，因此我们可以安全地使用+=运算符），并且在下一次迭代中注入该块返回的任何内容。因此，在这种情况下，我们必须显式返回哈希（total），以便在下一步中对其进行操作。

一个简单的例子是添加数组的所有值：

 [1,4,5,23,2,66,123].inject(0){|sum, value| sum += value}

[从0开始，我们执行0 + 1的第一个迭代，然后将其结果注入下一个迭代中。

注意：在您的原始代码中，您可以更轻松地遍历数组，而不是使用while循环和维护计数器，如下所示：

 alphabet.each do |single_char|
   single_char_count = file.count(single_char)
   print "#{alphabet[i]} = #{single_char_count} "
   alphabet.each do |second_char| 
     two_chars = single_char + second_char  
     # do something with two_chars 
     alphabet.each do |third_char|
       three_chars = single_char + second-char + third_char
       # do something with three_chars
     end 
   end
 end  

我猜想是迭代file（1-2-3）还是使用each_cons会更有效，这取决于file.scan的大小。