如何在Ruby中的哈希列表中为每个键提取更大的值 [英] How can I extract the bigger value for each key in a list of hashes in Ruby

问题描述

我可以想象有一个简单的方法来做，而不是使用许多变量和状态。

我只想得到为每个键给出的最高值散列列表

例如：

  > 19.4}，{1 => 12.4}，{2 => 29.4}，{3 => 12.4}，{2 => 39.4}，{2 => 59.4}] 
  
 
 
 
结果
  {1 => 19.4}，{3 => 12.4}，{2 => 59.4}] 
  
 
 
 
 
 
  a = [{1 = > 19.4}，{1 => 12.4}，{2 => 29.4}，{3 => 12.4}，{2 => 39.4}，{2 => 59.4}] 
 
＃下面是主要技巧，分组散列和排序键/值对
＃以**升序**。 
 a.sort_by（&：to_a）
＃=> [{1 => 12.4}，{1 => 19.4}，{2 => 29.4}，{2 => 39.4}，{2 => 59.4}，{3 => 12.4}] 
 
＃然后使用技巧，我们知道hash不能有重复的键，所以
＃盲目的我可以依靠`Enumerable＃inject`与`Hash＃merge`方法。 
 a.sort_by（&：to_a）.inject（：merge）
＃=> {1 => 19.4，2 => 59.4,3 => 12.4} 
 
＃final one 
 a.sort_by（&：to_a）.inject（：merge）。 map {| k，v | {k => v}} 
＃=> [{1 => 19.4}，{2 => 59.4}，{3 => 12.4}] 
  
 
I can imagine there is a simple way to do that instead of use many variables and state.

I just want to get the highest value given for each key in a list of hashes

For example:
[{1=>19.4}, {1=>12.4}, {2=>29.4}, {3=>12.4}, {2=>39.4}, {2=>59.4}]
Result
[{1=>19.4}, {3=>12.4}, {2=>59.4}]

解决方案
I'd do as below :
a = [{1=>19.4}, {1=>12.4}, {2=>29.4}, {3=>12.4}, {2=>39.4}, {2=>59.4}]

# the below is the main trick, to group the hashes and sorted the key/value pair
# in **ascending order**.
a.sort_by(&:to_a)
# => [{1=>12.4}, {1=>19.4}, {2=>29.4}, {2=>39.4}, {2=>59.4}, {3=>12.4}]

# then using the trick in mind, we know hash can't have duplicate keys, so
# blindly I can rely on `Enumerable#inject` with the `Hash#merge` method.
a.sort_by(&:to_a).inject(:merge)
# => {1=>19.4, 2=>59.4, 3=>12.4}

# final one
a.sort_by(&:to_a).inject(:merge).map { |k,v| {k => v} }
# => [{1=>19.4}, {2=>59.4}, {3=>12.4}]


                        
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