Ruby：反转哈希以保留非唯一值 [英] Ruby: Invert a hash to also preserve non unique values

问题描述

  {a=> [1,2,3]，b=> [4,5,6]，c=> [3,4,5]，d=> [7，2，3]} 
  

我想要做的是对所有现有的值与包含它的所有键的数组，例如将上面的内容转换为：

  {1 => [a]，2 => [a，d]，3 => [a，c，d]，4 => [b，c]} 
  

解决方案

I更喜欢@ Jikku的解决方案，但总有另一种方式。这是一个。

代码

  def inside_out（h）
g = h.flat_map {| s，a | a.product（[s]）} 
 .group_by（&：first）
 g.merge（g）{| _，a | a.map（& lt; last）} 
 end 
  

strong>

  h = {a=> [1,2,3]，b=> [4,5,6]，c=> [3,4,5]，d=> [7,2,3]} 
 
 inside_out（h）
＃=> {1 => [a]，2 => [a，d]，3 => [a，c，d]，4 => [b ，c]，
＃5 => [b，c]，6 => [b]，7 => [d]} 
  

说明

code> h 以上：

  a = h.flat_map {| s，a | a.product（[s]）} 
＃=> [[1，a]，[2，a]，[3，a]，[4，b]，[5，b]，[6，b]，
＃[3，c]，[4，c]，[5，c]，[7，d]，[2，d]，[3， ]] 
g = a.group_by（&第一个）
＃=> {1 => [[1，a]]，2 = [[2，a]，[2，d]]，
＃3 => [[ a]，[3，c]，[3，d]]，
＃4 => [[4，b]，[4，c]]，
＃5 => [[5，b]，[5，c]]，
＃6 => [[6，b]]，
＃ 7 => [[7，d]]} 
 g.merge（g）{| _，a | a.map（&; last）} 
＃=> {1 => [a]，2 => [a，d]，3 => [a，c，d]，4 => [b ，c]，
＃5 => [b，c]，6 => [b]，7 => [d]} 
  

I have a hash that looks like this:

{"a" => [1, 2, 3], "b" => [4, 5, 6], "c" => [3, 4, 5], "d" => [7, 2, 3]}

What I want to do is to make a hash of all existing values with an array of all keys that included it, e.g. turn the above into this:

{1 => ["a"], 2 => ["a", "d"], 3 => ["a", "c", "d"], 4 => ["b", "c"]}

解决方案

I do prefer @Jikku's solution, but there's always another way. Here's one. [Edit: I see this is very close to @Chris's solution. I will leave it for the last line, which is a little different.]

Code

def inside_out(h)
  g = h.flat_map { |s,a| a.product([s]) }
       .group_by(&:first)
  g.merge(g) { |_,a| a.map(&:last) }
end

Example

h = {"a" => [1, 2, 3], "b" => [4, 5, 6], "c" => [3, 4, 5], "d" => [7, 2, 3]}

inside_out(h)
  #=> {1=>["a"], 2=>["a", "d"], 3=>["a", "c", "d"], 4=>["b", "c"],
  #    5=>["b", "c"], 6=>["b"], 7=>["d"]} 

Explanation

For h above:

a = h.flat_map { |s,a| a.product([s]) }
  #=> [[1, "a"], [2, "a"], [3, "a"], [4, "b"], [5, "b"], [6, "b"],
  #    [3, "c"], [4, "c"], [5, "c"], [7, "d"], [2, "d"], [3, "d"]] 
g = a.group_by(&:first)
  #=> {1=>[[1, "a"]], 2=>[[2, "a"], [2, "d"]],
  #    3=>[[3, "a"], [3, "c"], [3, "d"]],
  #    4=>[[4, "b"], [4, "c"]],
  #    5=>[[5, "b"], [5, "c"]],
  #    6=>[[6, "b"]],
  #    7=>[[7, "d"]]} 
g.merge(g) { |_,a| a.map(&:last) }
  #=> {1=>["a"], 2=>["a", "d"], 3=>["a", "c", "d"], 4=>["b", "c"],
  #    5=>["b", "c"], 6=>["b"], 7=>["d"]} 

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